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  • int, short, byte performance in back-to-back for-loops

    - by runrunraygun
    (background: http://stackoverflow.com/questions/1097467/why-should-i-use-int-instead-of-a-byte-or-short-in-c) To satisfy my own curiosity about the pros and cons of using the "appropriate size" integer vs the "optimized" integer i wrote the following code which reinforced what I previously held true about int performance in .Net (and which is explained in the link above) which is that it is optimized for int performance rather than short or byte. DateTime t; long a, b, c; t = DateTime.Now; for (int index = 0; index < 127; index++) { Console.WriteLine(index.ToString()); } a = DateTime.Now.Ticks - t.Ticks; t = DateTime.Now; for (short index = 0; index < 127; index++) { Console.WriteLine(index.ToString()); } b=DateTime.Now.Ticks - t.Ticks; t = DateTime.Now; for (byte index = 0; index < 127; index++) { Console.WriteLine(index.ToString()); } c=DateTime.Now.Ticks - t.Ticks; Console.WriteLine(a.ToString()); Console.WriteLine(b.ToString()); Console.WriteLine(c.ToString()); This gives roughly consistent results in the area of... ~950000 ~2000000 ~1700000 which is in line with what i would expect to see. However when I try repeating the loops for each data type like this... t = DateTime.Now; for (int index = 0; index < 127; index++) { Console.WriteLine(index.ToString()); } for (int index = 0; index < 127; index++) { Console.WriteLine(index.ToString()); } for (int index = 0; index < 127; index++) { Console.WriteLine(index.ToString()); } a = DateTime.Now.Ticks - t.Ticks; the numbers are more like... ~4500000 ~3100000 ~300000 Which I find puzzling. Can anyone offer an explanation? NOTE: In the interest of compairing like for like i've limited the loops to 127 because of the range of the byte value type. Also this is an act of curiosity not production code micro-optimization.

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  • Printing an array in a method, from a different class?

    - by O.Lodhi
    Hello All, I'm a fairly inexperienced programmer, and i'm currently working on a Console Application project. It's basically a little 'mathematics game'; the application generates two random numbers, that have either been added, subtracted, multiplied or divided against each other randomly. The answer is shown on screen and the user has to pick from the menu which is the right mathematical operator, once the correct answer is picked the application then displays on screen how long it took for the user in milliseconds to input the correct answer. Now I want to save the times of the players in an array that can be called up later with all the scores. I need to include a method in this programme and I figured a method to save the times into an array would be suitable. I seem to have stumbled across a little problem though. I'm not quite sure what's wrong: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Mathgame { class Program { } class arrayclass { public static void saveInArray(int duration) { int[] TopTenScores = {000,1000,2000,3000,4000,5000,6000,7000,8000,9000}; if (duration < 1000) { duration = TopTenScores[000]; } else if ((duration >= 1000) && (duration <= 1999)) { duration = TopTenScores[1000]; } else if ((duration >= 2000) && (duration <= 2999)) { duration = TopTenScores[2000]; } else if ((duration >= 3000) && (duration <= 3999)) { duration = TopTenScores[3000]; } else if ((duration >= 4000) && (duration <= 4999)) { duration = TopTenScores[4000]; } else if ((duration >= 5000) && (duration <= 5999)) { duration = TopTenScores[5000]; } else if ((duration >= 6000) && (duration <= 6999)) { duration = TopTenScores[6000]; } else if ((duration >= 7000) && (duration <= 7999)) { duration = TopTenScores[7000]; } else if ((duration >= 8000) && (duration <= 8999)) { duration = TopTenScores[8000]; } else if ((duration >= 9000) && (duration <= 9999)) { duration = TopTenScores[9000]; } Console.WriteLine(TopTenScores); } static void Main(string[] args) { int intInput, num1, num2, incorrect, array1; float answer; string input; System.Random randNum = new System.Random(); Console.WriteLine("Welcome to the Maths game!"); Console.WriteLine("(Apologies for the glitchiness!)"); Console.WriteLine(); Console.WriteLine("Please choose from the following options:"); Console.WriteLine(); retry: Console.WriteLine("1 - Test your Maths against the clock!"); Console.WriteLine("2 - Exit the application."); Console.WriteLine("3 - Top scores"); Console.WriteLine(); input = Console.ReadLine(); intInput = int.Parse(input); if (intInput == 1) { goto start; } else if (intInput == 2) { goto fin; } else if (intInput == 3) { array1 = array1.saveInArray; goto retry; } Now, in the last 'else if' statement in the code, you can see my variable array1 trying to call the method, but no matter what I do I keep getting errors. This is the only error I have at the moment, but I have a feeling soon as I resolve that error, another will come up. For now i'm just determined to get past this error: 'int' does not contain a definition for 'saveInArray' and no extension method 'saveInArray' accepting a first argument of type 'int' could be found (are you missing a using directive or an assembly reference?). Any help would be kindly appreciated, apologies in advanced for my ugly written code! And thank you to any help that I receive! Regards, Omar.

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  • Why isn't the static constructor of the parent class called when invoking a method on a nested class

    - by Ryan Ische
    Given the following code, why isn't the static constructor of "Outer" called after the first line of "Main"? namespace StaticTester { class Program { static void Main( string[] args ) { Outer.Inner.Go(); Console.WriteLine(); Outer.Go(); Console.ReadLine(); } } public static partial class Outer { static Outer() { Console.Write( "In Outer's static constructor\n" ); } public static void Go() { Console.Write( "Outer Go\n" ); } public static class Inner { static Inner() { Console.Write( "In Inner's static constructor\n" ); } public static void Go() { Console.Write( "Inner Go\n" ); } } } }

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  • Time required for a process to complete

    - by yelkawar
    I am new to C# world. I am attempting to calculate time taken by a algorithum for the purpose of comparison. Following code measures the elapsed time from when a subroutine is called until the subroutine returns to the main program.This example is taken from "Data structures through C#" by Michael McMillan. After running this program the output is Time=0, which is incorrect. The program appears to be logically correct. Can anybody help me. Following is the code using System.Collections.Generic; using System.Collections; using System.Linq; using System.Text; namespace Chap1 { class Program { static void Main(string[] args) { int num1 = 100; int num2 = 200; Console.WriteLine("num1: " + num1); Console.WriteLine("num2: " + num2); Swap<int>(ref num1, ref num2); Console.WriteLine("num1: " + num1); Console.WriteLine("num2: " + num2); string str1 = "Sam"; string str2 = "Tom"; Console.WriteLine("String 1: " + str1); Console.WriteLine("String 2: " + str2); Swap<string>(ref str1, ref str2); Console.WriteLine("String 1: " + str1); Console.WriteLine("String 2: " + str2); Console.ReadKey(); } static void Swap<T>(ref T val1, ref T val2) { T temp; temp = val1; val1 = val2; val2 = temp; } } class Timing { TimeSpan StartTiming; TimeSpan duration; public Timing() { StartTiming = new TimeSpan(0); duration = new TimeSpan(0); } public TimeSpan startTime() { GC.Collect(); GC.WaitForPendingFinalizers(); StartTiming = Process.GetCurrentProcess().Threads[0].UserProcessorTime; return StartTiming; } public void stopTime() { duration = Process.GetCurrentProcess().Threads[0].UserProcessorTime.Subtract(StartTiming); } public TimeSpan result() { return duration; } } }

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  • C++ input chaining in C#

    - by Monty
    I am trying to learn C# coming from C++. I am writing just some basic console stuff to get a feel for it and was wondering if it is possible to do simple chaining of inputs in C#. For example in C++: cout<<"Enter two numbers: "; cin >> int1 >> int2; You could then just input 3 5 and hit enter and the values will be fine. In C# however I have to split it up(as far as I can tell) like this: Console.Write("Enter the first number: "; int1 = (char)Console.Read(); Console.Writeline(""); Console.Write("Enter the second number: "; int2 = (char)Console.Read(); Maybe I am just missing something.

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  • Javascript Prototyping Question

    - by Nick Lowman
    I'm just reading about Prototypes in JavaScript and Douglas Crockford offers and excellent way to select a new objects prototype but can anyone explain (below) why obj01's type equals 'object' when I pass it in function as it's prototype? if (typeof Object.beget !== 'function') { Object.beget = function (o) { console.log(typeof o);//function var F = function () {}; F.prototype = o; console.log(typeof F);//function return new F(); }; } var func01 = function(){}; var obj01 = Object.beget(func01); console.log(typeof obj01);//object console.log(typeof obj01.prototype);//object I thought it would be console.log(typeof obj01);//function console.log(typeof obj01.prototype);//function

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  • SQLite, python, unicode, and non-utf data

    - by Nathan Spears
    I started by trying to store strings in sqlite using python, and got the message: sqlite3.ProgrammingError: You must not use 8-bit bytestrings unless you use a text_factory that can interpret 8-bit bytestrings (like text_factory = str). It is highly recommended that you instead just switch your application to Unicode strings. Ok, I switched to Unicode strings. Then I started getting the message: sqlite3.OperationalError: Could not decode to UTF-8 column 'tag_artist' with text 'Sigur Rós' when trying to retrieve data from the db. More research and I started encoding it in utf8, but then 'Sigur Rós' starts looking like 'Sigur Rós' note: My console was set to display in 'latin_1' as @John Machin pointed out. What gives? After reading this, describing exactly the same situation I'm in, it seems as if the advice is to ignore the other advice and use 8-bit bytestrings after all. I didn't know much about unicode and utf before I started this process. I've learned quite a bit in the last couple hours, but I'm still ignorant of whether there is a way to correctly convert 'ó' from latin-1 to utf-8 and not mangle it. If there isn't, why would sqlite 'highly recommend' I switch my application to unicode strings? I'm going to update this question with a summary and some example code of everything I've learned in the last 24 hours so that someone in my shoes can have an easy(er) guide. If the information I post is wrong or misleading in any way please tell me and I'll update, or one of you senior guys can update. Summary of answers Let me first state the goal as I understand it. The goal in processing various encodings, if you are trying to convert between them, is to understand what your source encoding is, then convert it to unicode using that source encoding, then convert it to your desired encoding. Unicode is a base and encodings are mappings of subsets of that base. utf_8 has room for every character in unicode, but because they aren't in the same place as, for instance, latin_1, a string encoded in utf_8 and sent to a latin_1 console will not look the way you expect. In python the process of getting to unicode and into another encoding looks like: str.decode('source_encoding').encode('desired_encoding') or if the str is already in unicode str.encode('desired_encoding') For sqlite I didn't actually want to encode it again, I wanted to decode it and leave it in unicode format. Here are four things you might need to be aware of as you try to work with unicode and encodings in python. The encoding of the string you want to work with, and the encoding you want to get it to. The system encoding. The console encoding. The encoding of the source file Elaboration: (1) When you read a string from a source, it must have some encoding, like latin_1 or utf_8. In my case, I'm getting strings from filenames, so unfortunately, I could be getting any kind of encoding. Windows XP uses UCS-2 (a Unicode system) as its native string type, which seems like cheating to me. Fortunately for me, the characters in most filenames are not going to be made up of more than one source encoding type, and I think all of mine were either completely latin_1, completely utf_8, or just plain ascii (which is a subset of both of those). So I just read them and decoded them as if they were still in latin_1 or utf_8. It's possible, though, that you could have latin_1 and utf_8 and whatever other characters mixed together in a filename on Windows. Sometimes those characters can show up as boxes, other times they just look mangled, and other times they look correct (accented characters and whatnot). Moving on. (2) Python has a default system encoding that gets set when python starts and can't be changed during runtime. See here for details. Dirty summary ... well here's the file I added: \# sitecustomize.py \# this file can be anywhere in your Python path, \# but it usually goes in ${pythondir}/lib/site-packages/ import sys sys.setdefaultencoding('utf_8') This system encoding is the one that gets used when you use the unicode("str") function without any other encoding parameters. To say that another way, python tries to decode "str" to unicode based on the default system encoding. (3) If you're using IDLE or the command-line python, I think that your console will display according to the default system encoding. I am using pydev with eclipse for some reason, so I had to go into my project settings, edit the launch configuration properties of my test script, go to the Common tab, and change the console from latin-1 to utf-8 so that I could visually confirm what I was doing was working. (4) If you want to have some test strings, eg test_str = "ó" in your source code, then you will have to tell python what kind of encoding you are using in that file. (FYI: when I mistyped an encoding I had to ctrl-Z because my file became unreadable.) This is easily accomplished by putting a line like so at the top of your source code file: # -*- coding: utf_8 -*- If you don't have this information, python attempts to parse your code as ascii by default, and so: SyntaxError: Non-ASCII character '\xf3' in file _redacted_ on line 81, but no encoding declared; see http://www.python.org/peps/pep-0263.html for details Once your program is working correctly, or, if you aren't using python's console or any other console to look at output, then you will probably really only care about #1 on the list. System default and console encoding are not that important unless you need to look at output and/or you are using the builtin unicode() function (without any encoding parameters) instead of the string.decode() function. I wrote a demo function I will paste into the bottom of this gigantic mess that I hope correctly demonstrates the items in my list. Here is some of the output when I run the character 'ó' through the demo function, showing how various methods react to the character as input. My system encoding and console output are both set to utf_8 for this run: '?' = original char <type 'str'> repr(char)='\xf3' '?' = unicode(char) ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data 'ó' = char.decode('latin_1') <type 'unicode'> repr(char.decode('latin_1'))=u'\xf3' '?' = char.decode('utf_8') ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data Now I will change the system and console encoding to latin_1, and I get this output for the same input: 'ó' = original char <type 'str'> repr(char)='\xf3' 'ó' = unicode(char) <type 'unicode'> repr(unicode(char))=u'\xf3' 'ó' = char.decode('latin_1') <type 'unicode'> repr(char.decode('latin_1'))=u'\xf3' '?' = char.decode('utf_8') ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data Notice that the 'original' character displays correctly and the builtin unicode() function works now. Now I change my console output back to utf_8. '?' = original char <type 'str'> repr(char)='\xf3' '?' = unicode(char) <type 'unicode'> repr(unicode(char))=u'\xf3' '?' = char.decode('latin_1') <type 'unicode'> repr(char.decode('latin_1'))=u'\xf3' '?' = char.decode('utf_8') ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data Here everything still works the same as last time but the console can't display the output correctly. Etc. The function below also displays more information that this and hopefully would help someone figure out where the gap in their understanding is. I know all this information is in other places and more thoroughly dealt with there, but I hope that this would be a good kickoff point for someone trying to get coding with python and/or sqlite. Ideas are great but sometimes source code can save you a day or two of trying to figure out what functions do what. Disclaimers: I'm no encoding expert, I put this together to help my own understanding. I kept building on it when I should have probably started passing functions as arguments to avoid so much redundant code, so if I can I'll make it more concise. Also, utf_8 and latin_1 are by no means the only encoding schemes, they are just the two I was playing around with because I think they handle everything I need. Add your own encoding schemes to the demo function and test your own input. One more thing: there are apparently crazy application developers making life difficult in Windows. #!/usr/bin/env python # -*- coding: utf_8 -*- import os import sys def encodingDemo(str): validStrings = () try: print "str =",str,"{0} repr(str) = {1}".format(type(str), repr(str)) validStrings += ((str,""),) except UnicodeEncodeError as ude: print "Couldn't print the str itself because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t", print ude try: x = unicode(str) print "unicode(str) = ",x validStrings+= ((x, " decoded into unicode by the default system encoding"),) except UnicodeDecodeError as ude: print "ERROR. unicode(str) couldn't decode the string because the system encoding is set to an encoding that doesn't understand some character in the string." print "\tThe system encoding is set to {0}. See error:\n\t".format(sys.getdefaultencoding()), print ude except UnicodeEncodeError as uee: print "ERROR. Couldn't print the unicode(str) because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t", print uee try: x = str.decode('latin_1') print "str.decode('latin_1') =",x validStrings+= ((x, " decoded with latin_1 into unicode"),) try: print "str.decode('latin_1').encode('utf_8') =",str.decode('latin_1').encode('utf_8') validStrings+= ((x, " decoded with latin_1 into unicode and encoded into utf_8"),) except UnicodeDecodeError as ude: print "The string was decoded into unicode using the latin_1 encoding, but couldn't be encoded into utf_8. See error:\n\t", print ude except UnicodeDecodeError as ude: print "Something didn't work, probably because the string wasn't latin_1 encoded. See error:\n\t", print ude except UnicodeEncodeError as uee: print "ERROR. Couldn't print the str.decode('latin_1') because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t", print uee try: x = str.decode('utf_8') print "str.decode('utf_8') =",x validStrings+= ((x, " decoded with utf_8 into unicode"),) try: print "str.decode('utf_8').encode('latin_1') =",str.decode('utf_8').encode('latin_1') except UnicodeDecodeError as ude: print "str.decode('utf_8').encode('latin_1') didn't work. The string was decoded into unicode using the utf_8 encoding, but couldn't be encoded into latin_1. See error:\n\t", validStrings+= ((x, " decoded with utf_8 into unicode and encoded into latin_1"),) print ude except UnicodeDecodeError as ude: print "str.decode('utf_8') didn't work, probably because the string wasn't utf_8 encoded. See error:\n\t", print ude except UnicodeEncodeError as uee: print "ERROR. Couldn't print the str.decode('utf_8') because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t",uee print print "Printing information about each character in the original string." for char in str: try: print "\t'" + char + "' = original char {0} repr(char)={1}".format(type(char), repr(char)) except UnicodeDecodeError as ude: print "\t'?' = original char {0} repr(char)={1} ERROR PRINTING: {2}".format(type(char), repr(char), ude) except UnicodeEncodeError as uee: print "\t'?' = original char {0} repr(char)={1} ERROR PRINTING: {2}".format(type(char), repr(char), uee) print uee try: x = unicode(char) print "\t'" + x + "' = unicode(char) {1} repr(unicode(char))={2}".format(x, type(x), repr(x)) except UnicodeDecodeError as ude: print "\t'?' = unicode(char) ERROR: {0}".format(ude) except UnicodeEncodeError as uee: print "\t'?' = unicode(char) {0} repr(char)={1} ERROR PRINTING: {2}".format(type(x), repr(x), uee) try: x = char.decode('latin_1') print "\t'" + x + "' = char.decode('latin_1') {1} repr(char.decode('latin_1'))={2}".format(x, type(x), repr(x)) except UnicodeDecodeError as ude: print "\t'?' = char.decode('latin_1') ERROR: {0}".format(ude) except UnicodeEncodeError as uee: print "\t'?' = char.decode('latin_1') {0} repr(char)={1} ERROR PRINTING: {2}".format(type(x), repr(x), uee) try: x = char.decode('utf_8') print "\t'" + x + "' = char.decode('utf_8') {1} repr(char.decode('utf_8'))={2}".format(x, type(x), repr(x)) except UnicodeDecodeError as ude: print "\t'?' = char.decode('utf_8') ERROR: {0}".format(ude) except UnicodeEncodeError as uee: print "\t'?' = char.decode('utf_8') {0} repr(char)={1} ERROR PRINTING: {2}".format(type(x), repr(x), uee) print x = 'ó' encodingDemo(x) Much thanks for the answers below and especially to @John Machin for answering so thoroughly.

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  • SQLite, python, unicode, and non-utf data

    - by Nathan Spears
    I started by trying to store strings in sqlite using python, and got the message: sqlite3.ProgrammingError: You must not use 8-bit bytestrings unless you use a text_factory that can interpret 8-bit bytestrings (like text_factory = str). It is highly recommended that you instead just switch your application to Unicode strings. Ok, I switched to Unicode strings. Then I started getting the message: sqlite3.OperationalError: Could not decode to UTF-8 column 'tag_artist' with text 'Sigur Rós' when trying to retrieve data from the db. More research and I started encoding it in utf8, but then 'Sigur Rós' starts looking like 'Sigur Rós' note: My console was set to display in 'latin_1' as @John Machin pointed out. What gives? After reading this, describing exactly the same situation I'm in, it seems as if the advice is to ignore the other advice and use 8-bit bytestrings after all. I didn't know much about unicode and utf before I started this process. I've learned quite a bit in the last couple hours, but I'm still ignorant of whether there is a way to correctly convert 'ó' from latin-1 to utf-8 and not mangle it. If there isn't, why would sqlite 'highly recommend' I switch my application to unicode strings? I'm going to update this question with a summary and some example code of everything I've learned in the last 24 hours so that someone in my shoes can have an easy(er) guide. If the information I post is wrong or misleading in any way please tell me and I'll update, or one of you senior guys can update. Summary of answers Let me first state the goal as I understand it. The goal in processing various encodings, if you are trying to convert between them, is to understand what your source encoding is, then convert it to unicode using that source encoding, then convert it to your desired encoding. Unicode is a base and encodings are mappings of subsets of that base. utf_8 has room for every character in unicode, but because they aren't in the same place as, for instance, latin_1, a string encoded in utf_8 and sent to a latin_1 console will not look the way you expect. In python the process of getting to unicode and into another encoding looks like: str.decode('source_encoding').encode('desired_encoding') or if the str is already in unicode str.encode('desired_encoding') For sqlite I didn't actually want to encode it again, I wanted to decode it and leave it in unicode format. Here are four things you might need to be aware of as you try to work with unicode and encodings in python. The encoding of the string you want to work with, and the encoding you want to get it to. The system encoding. The console encoding. The encoding of the source file Elaboration: (1) When you read a string from a source, it must have some encoding, like latin_1 or utf_8. In my case, I'm getting strings from filenames, so unfortunately, I could be getting any kind of encoding. Windows XP uses UCS-2 (a Unicode system) as its native string type, which seems like cheating to me. Fortunately for me, the characters in most filenames are not going to be made up of more than one source encoding type, and I think all of mine were either completely latin_1, completely utf_8, or just plain ascii (which is a subset of both of those). So I just read them and decoded them as if they were still in latin_1 or utf_8. It's possible, though, that you could have latin_1 and utf_8 and whatever other characters mixed together in a filename on Windows. Sometimes those characters can show up as boxes, other times they just look mangled, and other times they look correct (accented characters and whatnot). Moving on. (2) Python has a default system encoding that gets set when python starts and can't be changed during runtime. See here for details. Dirty summary ... well here's the file I added: \# sitecustomize.py \# this file can be anywhere in your Python path, \# but it usually goes in ${pythondir}/lib/site-packages/ import sys sys.setdefaultencoding('utf_8') This system encoding is the one that gets used when you use the unicode("str") function without any other encoding parameters. To say that another way, python tries to decode "str" to unicode based on the default system encoding. (3) If you're using IDLE or the command-line python, I think that your console will display according to the default system encoding. I am using pydev with eclipse for some reason, so I had to go into my project settings, edit the launch configuration properties of my test script, go to the Common tab, and change the console from latin-1 to utf-8 so that I could visually confirm what I was doing was working. (4) If you want to have some test strings, eg test_str = "ó" in your source code, then you will have to tell python what kind of encoding you are using in that file. (FYI: when I mistyped an encoding I had to ctrl-Z because my file became unreadable.) This is easily accomplished by putting a line like so at the top of your source code file: # -*- coding: utf_8 -*- If you don't have this information, python attempts to parse your code as ascii by default, and so: SyntaxError: Non-ASCII character '\xf3' in file _redacted_ on line 81, but no encoding declared; see http://www.python.org/peps/pep-0263.html for details Once your program is working correctly, or, if you aren't using python's console or any other console to look at output, then you will probably really only care about #1 on the list. System default and console encoding are not that important unless you need to look at output and/or you are using the builtin unicode() function (without any encoding parameters) instead of the string.decode() function. I wrote a demo function I will paste into the bottom of this gigantic mess that I hope correctly demonstrates the items in my list. Here is some of the output when I run the character 'ó' through the demo function, showing how various methods react to the character as input. My system encoding and console output are both set to utf_8 for this run: '?' = original char <type 'str'> repr(char)='\xf3' '?' = unicode(char) ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data 'ó' = char.decode('latin_1') <type 'unicode'> repr(char.decode('latin_1'))=u'\xf3' '?' = char.decode('utf_8') ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data Now I will change the system and console encoding to latin_1, and I get this output for the same input: 'ó' = original char <type 'str'> repr(char)='\xf3' 'ó' = unicode(char) <type 'unicode'> repr(unicode(char))=u'\xf3' 'ó' = char.decode('latin_1') <type 'unicode'> repr(char.decode('latin_1'))=u'\xf3' '?' = char.decode('utf_8') ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data Notice that the 'original' character displays correctly and the builtin unicode() function works now. Now I change my console output back to utf_8. '?' = original char <type 'str'> repr(char)='\xf3' '?' = unicode(char) <type 'unicode'> repr(unicode(char))=u'\xf3' '?' = char.decode('latin_1') <type 'unicode'> repr(char.decode('latin_1'))=u'\xf3' '?' = char.decode('utf_8') ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data Here everything still works the same as last time but the console can't display the output correctly. Etc. The function below also displays more information that this and hopefully would help someone figure out where the gap in their understanding is. I know all this information is in other places and more thoroughly dealt with there, but I hope that this would be a good kickoff point for someone trying to get coding with python and/or sqlite. Ideas are great but sometimes source code can save you a day or two of trying to figure out what functions do what. Disclaimers: I'm no encoding expert, I put this together to help my own understanding. I kept building on it when I should have probably started passing functions as arguments to avoid so much redundant code, so if I can I'll make it more concise. Also, utf_8 and latin_1 are by no means the only encoding schemes, they are just the two I was playing around with because I think they handle everything I need. Add your own encoding schemes to the demo function and test your own input. One more thing: there are apparently crazy application developers making life difficult in Windows. #!/usr/bin/env python # -*- coding: utf_8 -*- import os import sys def encodingDemo(str): validStrings = () try: print "str =",str,"{0} repr(str) = {1}".format(type(str), repr(str)) validStrings += ((str,""),) except UnicodeEncodeError as ude: print "Couldn't print the str itself because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t", print ude try: x = unicode(str) print "unicode(str) = ",x validStrings+= ((x, " decoded into unicode by the default system encoding"),) except UnicodeDecodeError as ude: print "ERROR. unicode(str) couldn't decode the string because the system encoding is set to an encoding that doesn't understand some character in the string." print "\tThe system encoding is set to {0}. See error:\n\t".format(sys.getdefaultencoding()), print ude except UnicodeEncodeError as uee: print "ERROR. Couldn't print the unicode(str) because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t", print uee try: x = str.decode('latin_1') print "str.decode('latin_1') =",x validStrings+= ((x, " decoded with latin_1 into unicode"),) try: print "str.decode('latin_1').encode('utf_8') =",str.decode('latin_1').encode('utf_8') validStrings+= ((x, " decoded with latin_1 into unicode and encoded into utf_8"),) except UnicodeDecodeError as ude: print "The string was decoded into unicode using the latin_1 encoding, but couldn't be encoded into utf_8. See error:\n\t", print ude except UnicodeDecodeError as ude: print "Something didn't work, probably because the string wasn't latin_1 encoded. See error:\n\t", print ude except UnicodeEncodeError as uee: print "ERROR. Couldn't print the str.decode('latin_1') because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t", print uee try: x = str.decode('utf_8') print "str.decode('utf_8') =",x validStrings+= ((x, " decoded with utf_8 into unicode"),) try: print "str.decode('utf_8').encode('latin_1') =",str.decode('utf_8').encode('latin_1') except UnicodeDecodeError as ude: print "str.decode('utf_8').encode('latin_1') didn't work. The string was decoded into unicode using the utf_8 encoding, but couldn't be encoded into latin_1. See error:\n\t", validStrings+= ((x, " decoded with utf_8 into unicode and encoded into latin_1"),) print ude except UnicodeDecodeError as ude: print "str.decode('utf_8') didn't work, probably because the string wasn't utf_8 encoded. See error:\n\t", print ude except UnicodeEncodeError as uee: print "ERROR. Couldn't print the str.decode('utf_8') because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t",uee print print "Printing information about each character in the original string." for char in str: try: print "\t'" + char + "' = original char {0} repr(char)={1}".format(type(char), repr(char)) except UnicodeDecodeError as ude: print "\t'?' = original char {0} repr(char)={1} ERROR PRINTING: {2}".format(type(char), repr(char), ude) except UnicodeEncodeError as uee: print "\t'?' = original char {0} repr(char)={1} ERROR PRINTING: {2}".format(type(char), repr(char), uee) print uee try: x = unicode(char) print "\t'" + x + "' = unicode(char) {1} repr(unicode(char))={2}".format(x, type(x), repr(x)) except UnicodeDecodeError as ude: print "\t'?' = unicode(char) ERROR: {0}".format(ude) except UnicodeEncodeError as uee: print "\t'?' = unicode(char) {0} repr(char)={1} ERROR PRINTING: {2}".format(type(x), repr(x), uee) try: x = char.decode('latin_1') print "\t'" + x + "' = char.decode('latin_1') {1} repr(char.decode('latin_1'))={2}".format(x, type(x), repr(x)) except UnicodeDecodeError as ude: print "\t'?' = char.decode('latin_1') ERROR: {0}".format(ude) except UnicodeEncodeError as uee: print "\t'?' = char.decode('latin_1') {0} repr(char)={1} ERROR PRINTING: {2}".format(type(x), repr(x), uee) try: x = char.decode('utf_8') print "\t'" + x + "' = char.decode('utf_8') {1} repr(char.decode('utf_8'))={2}".format(x, type(x), repr(x)) except UnicodeDecodeError as ude: print "\t'?' = char.decode('utf_8') ERROR: {0}".format(ude) except UnicodeEncodeError as uee: print "\t'?' = char.decode('utf_8') {0} repr(char)={1} ERROR PRINTING: {2}".format(type(x), repr(x), uee) print x = 'ó' encodingDemo(x) Much thanks for the answers below and especially to @John Machin for answering so thoroughly.

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  • Creating packages in code - Package Configurations

    Continuing my theme of building various types of packages in code, this example shows how to building a package with package configurations. Incidentally it shows you how to add a variable, and a connection too. It covers the five most common configurations: Configuration File Indirect Configuration File SQL Server Indirect SQL Server Environment Variable  For a general overview try the SQL Server Books Online Package Configurations topic. The sample uses a a simple helper function ApplyConfig to create or update a configuration, although in the example we will only ever create. The most useful knowledge is the configuration string (Configuration.ConfigurationString) that you need to set. Configuration Type Configuration String Description Configuration File The full path and file name of an XML configuration file. The file can contain one or more configuration and includes the target path and new value to set. Indirect Configuration File An environment variable the value of which contains full path and file name of an XML configuration file as per the Configuration File type described above. SQL Server A three part configuration string, with each part being quote delimited and separated by a semi-colon. -- The first part is the connection manager name. The connection tells you which server and database to look for the configuration table. -- The second part is the name of the configuration table. The table is of a standard format, use the Package Configuration Wizard to help create an example, or see the sample script files below. The table contains one or more rows or configuration items each with a target path and new value. -- The third and final part is the optional filter name. A configuration table can contain multiple configurations, and the filter is  literal value that can be used to group items together and act as a filter clause when configurations are being read. If you do not need a filter, just leave the value empty. Indirect SQL Server An environment variable the value of which is the three part configuration string as per the SQL Server type described above. Environment Variable An environment variable the value of which is the value to set in the package. This is slightly different to the other examples as the configuration definition in the package also includes the target information. In our ApplyConfig function this is the only example that actually supplies a target value for the Configuration.PackagePath property. The path is an XPath style path for the target property, \Package.Variables[User::Variable].Properties[Value], the equivalent of which can be seen in the screenshot below, with the object being our variable called Variable, and the property to set is the Value property of that variable object. The configurations as seen when opening the generated package in BIDS: The sample code creates the package, adds a variable and connection manager, enables configurations, and then adds our example configurations. The package is then saved to disk, useful for checking the package and testing, before finally executing, just to prove it is valid. There are some external resources used here, namely some environment variables and a table, see below for more details. namespace Konesans.Dts.Samples { using System; using Microsoft.SqlServer.Dts.Runtime; public class PackageConfigurations { public void CreatePackage() { // Create a new package Package package = new Package(); package.Name = "ConfigurationSample"; // Add a variable, the target for our configurations package.Variables.Add("Variable", false, "User", 0); // Add a connection, for SQL configurations // Add the SQL OLE-DB connection ConnectionManager connectionManagerOleDb = package.Connections.Add("OLEDB"); connectionManagerOleDb.Name = "SQLConnection"; connectionManagerOleDb.ConnectionString = "Provider=SQLOLEDB.1;Data Source=(local);Initial Catalog=master;Integrated Security=SSPI;"; // Add our example configurations, first must enable package setting package.EnableConfigurations = true; // Direct configuration file, see sample file this.ApplyConfig(package, "Configuration File", DTSConfigurationType.ConfigFile, "C:\\Temp\\XmlConfig.dtsConfig", string.Empty); // Indirect configuration file, the emvironment variable XmlConfigFileEnvironmentVariable // contains the path to the configuration file, e.g. C:\Temp\XmlConfig.dtsConfig this.ApplyConfig(package, "Indirect Configuration File", DTSConfigurationType.IConfigFile, "XmlConfigFileEnvironmentVariable", string.Empty); // Direct SQL Server configuration, uses the SQLConnection package connection to read // configurations from the [dbo].[SSIS Configurations] table, with a filter of "SampleFilter" this.ApplyConfig(package, "SQL Server", DTSConfigurationType.SqlServer, "\"SQLConnection\";\"[dbo].[SSIS Configurations]\";\"SampleFilter\";", string.Empty); // Indirect SQL Server configuration, the environment variable "SQLServerEnvironmentVariable" // contains the configuration string e.g. "SQLConnection";"[dbo].[SSIS Configurations]";"SampleFilter"; this.ApplyConfig(package, "Indirect SQL Server", DTSConfigurationType.ISqlServer, "SQLServerEnvironmentVariable", string.Empty); // Direct environment variable, the value of the EnvironmentVariable environment variable is // applied to the target property, the value of the "User::Variable" package variable this.ApplyConfig(package, "EnvironmentVariable", DTSConfigurationType.EnvVariable, "EnvironmentVariable", "\\Package.Variables[User::Variable].Properties[Value]"); #if DEBUG // Save package to disk, DEBUG only new Application().SaveToXml(String.Format(@"C:\Temp\{0}.dtsx", package.Name), package, null); Console.WriteLine(@"C:\Temp\{0}.dtsx", package.Name); #endif // Execute package package.Execute(); // Basic check for warnings foreach (DtsWarning warning in package.Warnings) { Console.WriteLine("WarningCode : {0}", warning.WarningCode); Console.WriteLine(" SubComponent : {0}", warning.SubComponent); Console.WriteLine(" Description : {0}", warning.Description); Console.WriteLine(); } // Basic check for errors foreach (DtsError error in package.Errors) { Console.WriteLine("ErrorCode : {0}", error.ErrorCode); Console.WriteLine(" SubComponent : {0}", error.SubComponent); Console.WriteLine(" Description : {0}", error.Description); Console.WriteLine(); } package.Dispose(); } /// <summary> /// Add or update an package configuration. /// </summary> /// <param name="package">The package.</param> /// <param name="name">The configuration name.</param> /// <param name="type">The type of configuration</param> /// <param name="setting">The configuration setting.</param> /// <param name="target">The target of the configuration, leave blank if not required.</param> internal void ApplyConfig(Package package, string name, DTSConfigurationType type, string setting, string target) { Configurations configurations = package.Configurations; Configuration configuration; if (configurations.Contains(name)) { configuration = configurations[name]; } else { configuration = configurations.Add(); } configuration.Name = name; configuration.ConfigurationType = type; configuration.ConfigurationString = setting; configuration.PackagePath = target; } } } The following table lists the environment variables required for the full example to work along with some sample values. Variable Sample value EnvironmentVariable 1 SQLServerEnvironmentVariable "SQLConnection";"[dbo].[SSIS Configurations]";"SampleFilter"; XmlConfigFileEnvironmentVariable C:\Temp\XmlConfig.dtsConfig Sample code, package and configuration file. ConfigurationApplication.cs ConfigurationSample.dtsx XmlConfig.dtsConfig

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  • Parallel LINQ - PLINQ

    - by nmarun
    Turns out now with .net 4.0 we can run a query like a multi-threaded application. Say you want to query a collection of objects and return only those that meet certain conditions. Until now, we basically had one ‘control’ that iterated over all the objects in the collection, checked the condition on each object and returned if it passed. We obviously agree that if we can ‘break’ this task into smaller ones, assign each task to a different ‘control’ and ask all the controls to do their job - in-parallel, the time taken the finish the entire task will be much lower. Welcome to PLINQ. Let’s take some examples. I have the following method that uses our good ol’ LINQ. 1: private static void Linq(int lowerLimit, int upperLimit) 2: { 3: // populate an array with int values from lowerLimit to the upperLimit 4: var source = Enumerable.Range(lowerLimit, upperLimit); 5:  6: // Start a timer 7: Stopwatch stopwatch = new Stopwatch(); 8: stopwatch.Start(); 9:  10: // set the expectation => build the expression tree 11: var evenNumbers =   from num in source 12: where IsDivisibleBy(num, 2) 13: select num; 14: 15: // iterate over and print the returned items 16: foreach (var number in evenNumbers) 17: { 18: Console.WriteLine(string.Format("** {0}", number)); 19: } 20:  21: stopwatch.Stop(); 22:  23: // check the metrics 24: Console.WriteLine(String.Format("Elapsed {0}ms", stopwatch.ElapsedMilliseconds)); 25: } I’ve added comments for the major steps, but the only thing I want to talk about here is the IsDivisibleBy() method. I know I could have just included the logic directly in the where clause. I called a method to add ‘delay’ to the execution of the query - to simulate a loooooooooong operation (will be easier to compare the results). 1: private static bool IsDivisibleBy(int number, int divisor) 2: { 3: // iterate over some database query 4: // to add time to the execution of this method; 5: // the TableB has around 10 records 6: for (int i = 0; i < 10; i++) 7: { 8: DataClasses1DataContext dataContext = new DataClasses1DataContext(); 9: var query = from b in dataContext.TableBs select b; 10: 11: foreach (var row in query) 12: { 13: // Do NOTHING (wish my job was like this) 14: } 15: } 16:  17: return number % divisor == 0; 18: } Now, let’s look at how to modify this to PLINQ. 1: private static void Plinq(int lowerLimit, int upperLimit) 2: { 3: // populate an array with int values from lowerLimit to the upperLimit 4: var source = Enumerable.Range(lowerLimit, upperLimit); 5:  6: // Start a timer 7: Stopwatch stopwatch = new Stopwatch(); 8: stopwatch.Start(); 9:  10: // set the expectation => build the expression tree 11: var evenNumbers = from num in source.AsParallel() 12: where IsDivisibleBy(num, 2) 13: select num; 14:  15: // iterate over and print the returned items 16: foreach (var number in evenNumbers) 17: { 18: Console.WriteLine(string.Format("** {0}", number)); 19: } 20:  21: stopwatch.Stop(); 22:  23: // check the metrics 24: Console.WriteLine(String.Format("Elapsed {0}ms", stopwatch.ElapsedMilliseconds)); 25: } That’s it, this is now in PLINQ format. Oh and if you haven’t found the difference, look line 11 a little more closely. You’ll see an extension method ‘AsParallel()’ added to the ‘source’ variable. Couldn’t be more simpler right? So this is going to improve the performance for us. Let’s test it. So in my Main method of the Console application that I’m working on, I make a call to both. 1: static void Main(string[] args) 2: { 3: // set lower and upper limits 4: int lowerLimit = 1; 5: int upperLimit = 20; 6: // call the methods 7: Console.WriteLine("Calling Linq() method"); 8: Linq(lowerLimit, upperLimit); 9: 10: Console.WriteLine(); 11: Console.WriteLine("Calling Plinq() method"); 12: Plinq(lowerLimit, upperLimit); 13:  14: Console.ReadLine(); // just so I get enough time to read the output 15: } YMMV, but here are the results that I got:    It’s quite obvious from the above results that the Plinq() method is taking considerably less time than the Linq() version. I’m sure you’ve already noticed that the output of the Plinq() method is not in order. That’s because, each of the ‘control’s we sent to fetch the results, reported with values as and when they obtained them. This is something about parallel LINQ that one needs to remember – the collection cannot be guaranteed to be undisturbed. This could be counted as a negative about PLINQ (emphasize ‘could’). Nevertheless, if we want the collection to be sorted, we can use a SortedSet (.net 4.0) or build our own custom ‘sorter’. Either way we go, there’s a good chance we’ll end up with a better performance using PLINQ. And there’s another negative of PLINQ (depending on how you see it). This is regarding the CPU cycles. See the usage for Linq() method (used ResourceMonitor): I have dual CPU’s and see the height of the peak in the bottom two blocks and now compare to what happens when I run the Plinq() method. The difference is obvious. Higher usage, but for a shorter duration (width of the peak). Both these points make sense in both cases. Linq() runs for a longer time, but uses less resources whereas Plinq() runs for a shorter time and consumes more resources. Even after knowing all these, I’m still inclined towards PLINQ. PLINQ rocks! (no hard feelings LINQ)

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  • Code refactoring with Visual Studio 2010 Part-2

    - by Jalpesh P. Vadgama
    In previous post I have written about Extract Method Code refactoring option. In this post I am going to some other code refactoring features of Visual Studio 2010.  Renaming variables and methods is one of the most difficult task for a developer. Normally we do like this. First we will rename method or variable and then we will find all the references then do remaining over that stuff. This will be become difficult if your variable or method are referenced at so many files and so many place. But once you use refactor menu rename it will be bit Easy. I am going to use same code which I have created in my previous post. I am just once again putting that code here for your reference. using System; namespace CodeRefractoring { class Program { static void Main(string[] args) { string firstName = "Jalpesh"; string lastName = "Vadgama"; Print(firstName, lastName); } private static void Print(string firstName, string lastName) { Console.WriteLine(string.Format("FirstName:{0}", firstName)); Console.WriteLine(string.Format("LastName:{0}", lastName)); Console.ReadLine(); } } } Now I want to rename print method in this code. To rename the method you can select method name and then select Refactor-> Rename . Once I selected Print method and then click on rename a dialog box will appear like following. Now I am renaming this Print method to PrintMyName like following.   Now once you click OK a dialog will appear with preview of code like following. It will show preview of code. Now once you click apply. You code will be changed like following. using System; namespace CodeRefractoring { class Program { static void Main(string[] args) { string firstName = "Jalpesh"; string lastName = "Vadgama"; PrintMyName(firstName, lastName); } private static void PrintMyName(string firstName, string lastName) { Console.WriteLine(string.Format("FirstName:{0}", firstName)); Console.WriteLine(string.Format("LastName:{0}", lastName)); Console.ReadLine(); } } } So that’s it. This will work in multiple files also. Hope you liked it.. Stay tuned for more.. Till that Happy Programming.

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  • Finding an alert in the middle of your javascript

    - by Ariel Popovsky
    I was debugging a script injection issue the other day using some sample code with an alert in it. The alert was popping out meaning the code got executed leaving open the possibility for a hacker to put there some nasty malicious code. I knew my alert was being executed but didn’t know how. So I tried something that worked perfectly for this problem, replaced the native alert function with my own one. All I had to do in Chrome was open the javascript console and type: alert = function(msg){ console.log(msg); console.trace(); }; The next time the malicious code was executed, instead of the regular alert I got something similar to this:   alert("testing") testing console.trace() alert:2 (anonymous function):2 InjectedScript._evaluateOn:312 InjectedScript._evaluateAndWrap:294 InjectedScript.evaluate:288 undefined In my case I was able to see what was going on and find the offending function. This was tested on Firebug in Firefox and it works as.

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  • Tutorial: Getting Started with the NoSQL JavaScript / Node.js API for MySQL Cluster

    - by Mat Keep
    Tutorial authored by Craig Russell and JD Duncan  The MySQL Cluster team are working on a new NoSQL JavaScript connector for MySQL. The objectives are simplicity and high performance for JavaScript users: - allows end-to-end JavaScript development, from the browser to the server and now to the world's most popular open source database - native "NoSQL" access to the storage layer without going first through SQL transformations and parsing. Node.js is a complete web platform built around JavaScript designed to deliver millions of client connections on commodity hardware. With the MySQL NoSQL Connector for JavaScript, Node.js users can easily add data access and persistence to their web, cloud, social and mobile applications. While the initial implementation is designed to plug and play with Node.js, the actual implementation doesn't depend heavily on Node, potentially enabling wider platform support in the future. Implementation The architecture and user interface of this connector are very different from other MySQL connectors in a major way: it is an asynchronous interface that follows the event model built into Node.js. To make it as easy as possible, we decided to use a domain object model to store the data. This allows for users to query data from the database and have a fully-instantiated object to work with, instead of having to deal with rows and columns of the database. The domain object model can have any user behavior that is desired, with the NoSQL connector providing the data from the database. To make it as fast as possible, we use a direct connection from the user's address space to the database. This approach means that no SQL (pun intended) is needed to get to the data, and no SQL server is between the user and the data. The connector is being developed to be extensible to multiple underlying database technologies, including direct, native access to both the MySQL Cluster "ndb" and InnoDB storage engines. The connector integrates the MySQL Cluster native API library directly within the Node.js platform itself, enabling developers to seamlessly couple their high performance, distributed applications with a high performance, distributed, persistence layer delivering 99.999% availability. The following sections take you through how to connect to MySQL, query the data and how to get started. Connecting to the database A Session is the main user access path to the database. You can get a Session object directly from the connector using the openSession function: var nosql = require("mysql-js"); var dbProperties = {     "implementation" : "ndb",     "database" : "test" }; nosql.openSession(dbProperties, null, onSession); The openSession function calls back into the application upon creating a Session. The Session is then used to create, delete, update, and read objects. Reading data The Session can read data from the database in a number of ways. If you simply want the data from the database, you provide a table name and the key of the row that you want. For example, consider this schema: create table employee (   id int not null primary key,   name varchar(32),   salary float ) ENGINE=ndbcluster; Since the primary key is a number, you can provide the key as a number to the find function. function onSession = function(err, session) {   if (err) {     console.log(err);     ... error handling   }   session.find('employee', 0, onData); }; function onData = function(err, data) {   if (err) {     console.log(err);     ... error handling   }   console.log('Found: ', JSON.stringify(data));   ... use data in application }; If you want to have the data stored in your own domain model, you tell the connector which table your domain model uses, by specifying an annotation, and pass your domain model to the find function. var annotations = new nosql.Annotations(); function Employee = function(id, name, salary) {   this.id = id;   this.name = name;   this.salary = salary;   this.giveRaise = function(percent) {     this.salary *= percent;   } }; annotations.mapClass(Employee, {'table' : 'employee'}); function onSession = function(err, session) {   if (err) {     console.log(err);     ... error handling   }   session.find(Employee, 0, onData); }; Updating data You can update the emp instance in memory, but to make the raise persistent, you need to write it back to the database, using the update function. function onData = function(err, emp) {   if (err) {     console.log(err);     ... error handling   }   console.log('Found: ', JSON.stringify(emp));   emp.giveRaise(0.12); // gee, thanks!   session.update(emp); // oops, session is out of scope here }; Using JavaScript can be tricky because it does not have the concept of block scope for variables. You can create a closure to handle these variables, or use a feature of the connector to remember your variables. The connector api takes a fixed number of parameters and returns a fixed number of result parameters to the callback function. But the connector will keep track of variables for you and return them to the callback. So in the above example, change the onSession function to remember the session variable, and you can refer to it in the onData function: function onSession = function(err, session) {   if (err) {     console.log(err);     ... error handling   }   session.find(Employee, 0, onData, session); }; function onData = function(err, emp, session) {   if (err) {     console.log(err);     ... error handling   }   console.log('Found: ', JSON.stringify(emp));   emp.giveRaise(0.12); // gee, thanks!   session.update(emp, onUpdate); // session is now in scope }; function onUpdate = function(err, emp) {   if (err) {     console.log(err);     ... error handling   } Inserting data Inserting data requires a mapped JavaScript user function (constructor) and a session. Create a variable and persist it: function onSession = function(err, session) {   var data = new Employee(999, 'Mat Keep', 20000000);   session.persist(data, onInsert);   } }; Deleting data To remove data from the database, use the session remove function. You use an instance of the domain object to identify the row you want to remove. Only the key field is relevant. function onSession = function(err, session) {   var key = new Employee(999);   session.remove(Employee, onDelete);   } }; More extensive queries We are working on the implementation of more extensive queries along the lines of the criteria query api. Stay tuned. How to evaluate The MySQL Connector for JavaScript is available for download from labs.mysql.com. Select the build: MySQL-Cluster-NoSQL-Connector-for-Node-js You can also clone the project on GitHub Since it is still early in development, feedback is especially valuable (so don't hesitate to leave comments on this blog, or head to the MySQL Cluster forum). Try it out and see how easy (and fast) it is to integrate MySQL Cluster into your Node.js platforms. You can learn more about other previewed functionality of MySQL Cluster 7.3 here

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  • Creating Property Set Expression Trees In A Developer Friendly Way

    - by Paulo Morgado
    In a previous post I showed how to create expression trees to set properties on an object. The way I did it was not very developer friendly. It involved explicitly creating the necessary expressions because the compiler won’t generate expression trees with property or field set expressions. Recently someone contacted me the help develop some kind of command pattern framework that used developer friendly lambdas to generate property set expression trees. Simply putting, given this entity class: public class Person { public string Name { get; set; } } The person in question wanted to write code like this: var et = Set((Person p) => p.Name = "me"); Where et is the expression tree that represents the property assignment. So, if we can’t do this, let’s try the next best thing that is splitting retrieving the property information from the retrieving the value to assign o the property: var et = Set((Person p) => p.Name, () => "me"); And this is something that the compiler can handle. The implementation of Set receives an expression to retrieve the property information from and another expression the retrieve the value to assign to the property: public static Expression<Action<TEntity>> Set<TEntity, TValue>( Expression<Func<TEntity, TValue>> propertyGetExpression, Expression<Func<TValue>> valueExpression) The implementation of this method gets the property information form the body of the property get expression (propertyGetExpression) and the value expression (valueExpression) to build an assign expression and builds a lambda expression using the same parameter of the property get expression as its parameter: public static Expression<Action<TEntity>> Set<TEntity, TValue>( Expression<Func<TEntity, TValue>> propertyGetExpression, Expression<Func<TValue>> valueExpression) { var entityParameterExpression = (ParameterExpression)(((MemberExpression)(propertyGetExpression.Body)).Expression); return Expression.Lambda<Action<TEntity>>( Expression.Assign(propertyGetExpression.Body, valueExpression.Body), entityParameterExpression); } And now we can use the expression to translate to another context or just compile and use it: var et = Set((Person p) => p.Name, () => name); Console.WriteLine(person.Name); // Prints: p => (p.Name = “me”) var d = et.Compile(); d(person); Console.WriteLine(person.Name); // Prints: me It can even support closures: var et = Set((Person p) => p.Name, () => name); Console.WriteLine(person.Name); // Prints: p => (p.Name = value(<>c__DisplayClass0).name) var d = et.Compile(); name = "me"; d(person); Console.WriteLine(person.Name); // Prints: me name = "you"; d(person); Console.WriteLine(person.Name); // Prints: you Not so useful in the intended scenario (but still possible) is building an expression tree that receives the value to assign to the property as a parameter: public static Expression<Action<TEntity, TValue>> Set<TEntity, TValue>(Expression<Func<TEntity, TValue>> propertyGetExpression) { var entityParameterExpression = (ParameterExpression)(((MemberExpression)(propertyGetExpression.Body)).Expression); var valueParameterExpression = Expression.Parameter(typeof(TValue)); return Expression.Lambda<Action<TEntity, TValue>>( Expression.Assign(propertyGetExpression.Body, valueParameterExpression), entityParameterExpression, valueParameterExpression); } This new expression can be used like this: var et = Set((Person p) => p.Name); Console.WriteLine(person.Name); // Prints: (p, Param_0) => (p.Name = Param_0) var d = et.Compile(); d(person, "me"); Console.WriteLine(person.Name); // Prints: me d(person, "you"); Console.WriteLine(person.Name); // Prints: you The only caveat is that we need to be able to write code to read the property in order to write to it.

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  • How to use the client object model with SharePoint2010

    - by ybbest
    In SharePoint2010, you can use client object model to communicate with SharePoint server. Today, I’d like to show you how to achieve this by using the c# console application. You can download the solution here. 1. Create a Console application in visual studio and add the following references to the project. 2. Insert your code as below ClientContext context = new ClientContext("http://demo2010a"); Web currentWeb = context.Web; context.Load(currentWeb, web =&gt; web.Title); context.ExecuteQuery(); Console.WriteLine(currentWeb.Title); Console.ReadLine(); 3. Run your code then you will get the web title displayed as shown below Note: If you got the following errors, you need to change your target framework from .Net Framework 4 client profile to .Net Framework 4 as shown below: Change from TO

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  • Beware of const members

    - by nmarun
    I happened to learn a new thing about const today and how one needs to be careful with its usage. Let’s say I have a third-party assembly ‘ConstVsReadonlyLib’ with a class named ConstSideEffect.cs: 1: public class ConstSideEffect 2: { 3: public static readonly int StartValue = 10; 4: public const int EndValue = 20; 5: } In my project, I reference the above assembly as follows: 1: static void Main(string[] args) 2: { 3: for (int i = ConstSideEffect.StartValue; i < ConstSideEffect.EndValue; i++) 4: { 5: Console.WriteLine(i); 6: } 7: Console.ReadLine(); 8: } You’ll see values 10 through 19 as expected. Now, let’s say I receive a new version of the ConstVsReadonlyLib. 1: public class ConstSideEffect 2: { 3: public static readonly int StartValue = 5; 4: public const int EndValue = 30; 5: } If I just drop this new assembly in the bin folder and run the application, without rebuilding my console application, my thinking was that the output would be from 5 to 29. Of course I was wrong… if not you’d not be reading this blog. The actual output is from 5 through 19. The reason is due to the behavior of const and readonly members. To begin with, const is the compile-time constant and readonly is a runtime constant. Next, when you compile the code, a compile-time constant member is replaced with the value of the constant in the code. But, the IL generated when you reference a read-only constant, references the readonly variable, not its value. So, the IL version of the Main method, after compilation actually looks something like: 1: static void Main(string[] args) 2: { 3: for (int i = ConstSideEffect.StartValue; i < 20; i++) 4: { 5: Console.WriteLine(i); 6: } 7: Console.ReadLine(); 8: } I’m no expert with this IL thingi, but when I look at the disassembled code of the exe file (using IL Disassembler), I see the following: I see our readonly member still being referenced by the variable name (ConstVsReadonlyLib.ConstSideEffect::StartValue) in line 0001. Then there’s the Console.WriteLine in line 000b and finally, see the value of 20 in line 0017. This, I’m pretty sure is our const member being replaced by its value which marks the upper bound of the ‘for’ loop. Now you know why the output was from 5 through 19. This definitely is a side-effect of having const members and one needs to be aware of it. While we’re here, I’d like to add a few other points about const and readonly members: const is slightly faster, but is less flexible readonly cannot be declared within a method scope const can be used only on primitive types (numbers and strings) Just wanted to share this before going to bed!

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  • Subterranean IL: Exception handler semantics

    - by Simon Cooper
    In my blog posts on fault and filter exception handlers, I said that the same behaviour could be replicated using normal catch blocks. Well, that isn't entirely true... Changing the handler semantics Consider the following: .try { .try { .try { newobj instance void [mscorlib]System.Exception::.ctor() // IL for: // e.Data.Add("DictKey", true) throw } fault { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) endfault } } filter { ldstr "2a: Filter logic" call void [mscorlib]System.Console::WriteLine(string) // IL for: // (bool)((Exception)e).Data["DictKey"] endfilter }{ ldstr "2b: Filter handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } } catch object { ldstr "3: Catch handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } Return: // rest of method If the filter handler is engaged (true is inserted into the exception dictionary) then the filter handler gets engaged, and the following gets printed to the console: 2a: Filter logic 1: Fault handler 2b: Filter handler and if the filter handler isn't engaged, then the following is printed: 2a:Filter logic 1: Fault handler 3: Catch handler Filter handler execution The filter handler is executed first. Hmm, ok. Well, what happens if we replaced the fault block with the C# equivalent (with the exception dictionary value set to false)? .try { // throw exception } catch object { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) rethrow } we get this: 1: Fault handler 2a: Filter logic 3: Catch handler The fault handler is executed first, instead of the filter block. Eh? This change in behaviour is due to the way the CLR searches for exception handlers. When an exception is thrown, the CLR stops execution of the thread, and searches up the stack for an exception handler that can handle the exception and stop it propagating further - catch or filter handlers. It checks the type clause of catch clauses, and executes the code in filter blocks to see if the filter can handle the exception. When the CLR finds a valid handler, it saves the handler's location, then goes back to where the exception was thrown and executes fault and finally blocks between there and the handler location, discarding stack frames in the process, until it reaches the handler. So? By replacing a fault with a catch, we have changed the semantics of when the filter code is executed; by using a rethrow instruction, we've split up the exception handler search into two - one search to find the first catch, then a second when the rethrow instruction is encountered. This is only really obvious when mixing C# exception handlers with fault or filter handlers, so this doesn't affect code written only in C#. However it could cause some subtle and hard-to-debug effects with object initialization and ordering when using and calling code written in a language that can compile fault and filter handlers.

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  • Keypress detection wont work after seemingly unrelated code change

    - by LukeZaz
    I'm trying to have the Enter key cause a new 'map' to generate for my game, but for whatever reason after implementing full-screen in it the input check won't work anymore. I tried removing the new code and only pressing one key at a time, but it still won't work. Here's the check code and the method it uses, along with the newMap method: public class Game1 : Microsoft.Xna.Framework.Game { // ... protected override void Update(GameTime gameTime) { // ... // Check if Enter was pressed - if so, generate a new map if (CheckInput(Keys.Enter, 1)) { blocks = newMap(map, blocks, console); } // ... } // Method: Checks if a key is/was pressed public bool CheckInput(Keys key, int checkType) { // Get current keyboard state KeyboardState newState = Keyboard.GetState(); bool retType = false; // Return type if (checkType == 0) { // Check Type: Is key currently down? if (newState.IsKeyDown(key)) { retType = true; } else { retType = false; } } else if (checkType == 1) { // Check Type: Was the key pressed? if (newState.IsKeyDown(key)) { if (!oldState.IsKeyDown(key)) { // Key was just pressed retType = true; } else { // Key was already pressed, return false retType = false; } } } // Save keyboard state oldState = newState; // Return result if (retType == true) { return true; } else { return false; } } // Method: Generate a new map public List<Block> newMap(Map map, List<Block> blockList, Console console) { // Create new map block coordinates List<Vector2> positions = new List<Vector2>(); positions = map.generateMap(console); // Clear list and reallocate memory previously used up by it blockList.Clear(); blockList.TrimExcess(); // Add new blocks to the list using positions created by generateMap() foreach (Vector2 pos in positions) { blockList.Add(new Block() { Position = pos, Texture = dirtTex }); } // Return modified list return blockList; } // ... } and the generateMap code: // Generate a list of Vector2 positions for blocks public List<Vector2> generateMap(Console console, int method = 0) { ScreenTileWidth = gDevice.Viewport.Width / 16; ScreenTileHeight = gDevice.Viewport.Height / 16; maxHeight = gDevice.Viewport.Height; List<Vector2> blockLocations = new List<Vector2>(); if (useScreenSize == true) { Width = ScreenTileWidth; Height = ScreenTileHeight; } else { maxHeight = Height; } int startHeight = -500; // For debugging purposes, the startHeight is set to an // hopefully-unreachable value - if it returns this, something is wrong // Methods of land generation /// <summary> /// Third version land generation /// Generates a base land height as the second version does /// but also generates a 'max change' value which determines how much /// the land can raise or lower by which it now does by a random amount /// during generation /// </summary> if (method == 0) { // Get the land height startHeight = rnd.Next(1, maxHeight); int maxChange = rnd.Next(1, 5); // Amount ground will raise/lower by int curHeight = startHeight; for (int w = 0; w < Width; w++) { // Run a chance to lower/raise ground level int changeBy = rnd.Next(1, maxChange); int doChange = rnd.Next(0, 3); if (doChange == 1 && !(curHeight <= (1 + maxChange))) { curHeight = curHeight - changeBy; } else if (doChange == 2 && !(curHeight >= (29 - maxChange))) { curHeight = curHeight + changeBy; } for (int h = curHeight; h < Height; h++) { // Location variables float x = w * 16; float y = h * 16; blockLocations.Add(new Vector2(x, y)); } } console.newMsg("[INFO] Cur, height change maximum: " + maxChange.ToString()); } /// <summary> /// Second version land generator /// Generates a solid mass of land starting at a random height /// derived from either screen height or provided height value /// </summary> else if (method == 1) { // Get the land height startHeight = rnd.Next(0, 30); for (int w = 0; w < Width; w++) { for (int h = startHeight; h < ScreenTileHeight; h++) { // Location variables float x = w * 16; float y = h * 16; // Add a tile at set location blockLocations.Add(new Vector2(x, y)); } } } /// <summary> /// First version land generator /// Generates land completely randomly either across screen or /// in a box set by Width and Height values /// </summary> else { // For each tile in the map... for (int w = 0; w < Width; w++) { for (int h = 0; h < Height; h++) { // Location variables float x = w * 16; float y = h * 16; // ...decide whether or not to place a tile... if (rnd.Next(0, 2) == 1) { // ...and if so, add a tile at that location. blockLocations.Add(new Vector2(x, y)); } } } } console.newMsg("[INFO] Cur, base height: " + startHeight.ToString()); return blockLocations; } I never touched any of the above code for this when it broke - changing keys won't seem to fix it. Despite this, I have camera movement set inside another Game1 method that uses WASD and works perfectly. All I did was add a few lines of code here: private int BackBufferWidth = 1280; // Added these variables private int BackBufferHeight = 800; public Game1() { graphics = new GraphicsDeviceManager(this); graphics.PreferredBackBufferWidth = BackBufferWidth; // and this graphics.PreferredBackBufferHeight = BackBufferHeight; // this Content.RootDirectory = "Content"; this.graphics.IsFullScreen = true; // and this } When I try adding a console line to be printed in the event the key is pressed, it seems that the If is never even triggered despite the correct key being pressed.

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  • await, WhenAll, WaitAll, oh my!!

    - by cibrax
    If you are dealing with asynchronous work in .NET, you might know that the Task class has become the main driver for wrapping asynchronous calls. Although this class was officially introduced in .NET 4.0, the programming model for consuming tasks was much more simplified in C# 5.0 in .NET 4.5 with the addition of the new async/await keywords. In a nutshell, you can use these keywords to make asynchronous calls as if they were sequential, and avoiding in that way any fork or callback in the code. The compiler takes care of the rest. I was yesterday writing some code for making multiple asynchronous calls to backend services in parallel. The code looked as follow, var allResults = new List<Result>(); foreach(var provider in providers) { var results = await provider.GetResults(); allResults.AddRange(results); } return allResults; You see, I was using the await keyword to make multiple calls in parallel. Something I did not consider was the overhead this code implied after being compiled. I started an interesting discussion with some smart folks in twitter. One of them, Tugberk Ugurlu, had the brilliant idea of actually write some code to make a performance comparison with another approach using Task.WhenAll. There are two additional methods you can use to wait for the results of multiple calls in parallel, WhenAll and WaitAll. WhenAll creates a new task and waits for results in that new task, so it does not block the calling thread. WaitAll, on the other hand, blocks the calling thread. This is the code Tugberk initially wrote, and I modified afterwards to also show the results of WaitAll. class Program { private static Func<Stopwatch, Task>[] funcs = new Func<Stopwatch, Task>[] { async (watch) => { watch.Start(); await Task.Delay(1000); Console.WriteLine("1000 one has been completed."); }, async (watch) => { await Task.Delay(1500); Console.WriteLine("1500 one has been completed."); }, async (watch) => { await Task.Delay(2000); Console.WriteLine("2000 one has been completed."); watch.Stop(); Console.WriteLine(watch.ElapsedMilliseconds + "ms has been elapsed."); } }; static void Main(string[] args) { Console.WriteLine("Await in loop work starts..."); DoWorkAsync().ContinueWith(task => { Console.WriteLine("Parallel work starts..."); DoWorkInParallelAsync().ContinueWith(t => { Console.WriteLine("WaitAll work starts..."); WaitForAll(); }); }); Console.ReadLine(); } static async Task DoWorkAsync() { Stopwatch watch = new Stopwatch(); foreach (var func in funcs) { await func(watch); } } static async Task DoWorkInParallelAsync() { Stopwatch watch = new Stopwatch(); await Task.WhenAll(funcs[0](watch), funcs[1](watch), funcs[2](watch)); } static void WaitForAll() { Stopwatch watch = new Stopwatch(); Task.WaitAll(funcs[0](watch), funcs[1](watch), funcs[2](watch)); } } After running this code, the results were very concluding. Await in loop work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 4532ms has been elapsed. Parallel work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 2007ms has been elapsed. WaitAll work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 2009ms has been elapsed. The await keyword in a loop does not really make the calls in parallel.

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  • Implicit and Explicit implementations for Multiple Interface inheritance

    Following C#.NET demo explains you all the scenarios for implementation of Interface methods to classes. There are two ways you can implement a interface method to a class. 1. Implicit Implementation 2. Explicit Implementation. Please go though the sample. using System; namespace ImpExpTest {     class Program     {         static void Main(string[] args)         {             C o3 = new C();             Console.WriteLine(o3.fu());             I1 o1 = new C();             Console.WriteLine(o1.fu());             I2 o2 = new C();             Console.WriteLine(o2.fu());             var o4 = new C();       //var is considered as C             Console.WriteLine(o4.fu());             var o5 = (I1)new C();   //var is considered as I1             Console.WriteLine(o5.fu());             var o6 = (I2)new C();   //var is considered as I2             Console.WriteLine(o6.fu());             D o7 = new D();             Console.WriteLine(o7.fu());             I1 o8 = new D();             Console.WriteLine(o8.fu());             I2 o9 = new D();             Console.WriteLine(o9.fu());         }     }     interface I1     {         string fu();     }     interface I2     {         string fu();     }     class C : I1, I2     {         #region Imicitly Defined I1 Members         public string fu()         {             return "Hello C"         }         #endregion Imicitly Defined I1 Members         #region Explicitly Defined I1 Members         string I1.fu()         {             return "Hello from I1";         }         #endregion Explicitly Defined I1 Members         #region Explicitly Defined I2 Members         string I2.fu()         {             return "Hello from I2";         }         #endregion Explicitly Defined I2 Members     }     class D : C     {         #region Imicitly Defined I1 Members         public string fu()         {             return "Hello from D";         }         #endregion Imicitly Defined I1 Members     } } Output:- Hello C Hello from I1 Hello from I2 Hello C Hello from I1 Hello from I2 Hello from D Hello from I1 Hello from I2 span.fullpost {display:none;}

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  • Image first loaded, then it isn't? (XNA)

    - by M0rgenstern
    I am very confused at the Moment. I have the following Class: (Just a part of the class): public class GUIWindow { #region Static Fields //The standard image for windows. public static IngameImage StandardBackgroundImage; #endregion } IngameImage is just one of my own classes, but actually it contains a Texture2D (and some other things). In another class I load a list of GUIButtons by deserializing a XML file. public static GUI Initializazion(string pXMLPath, ContentManager pConMan) { GUI myGUI = pConMan.Load<GUI>(pXMLPath); GUIWindow.StandardBackgroundImage = new IngameImage(pConMan.Load<Texture2D>(myGUI.WindowStandardBackgroundImagePath), Vector2.Zero, 1024, 600, 1, 0, Color.White, 1.0f, true, false, false); System.Console.WriteLine("Image loaded? " + (GUIWindow.StandardBackgroundImage.ImageStrip != null)); myGUI.Windows = pConMan.Load<List<GUIWindow>>(myGUI.GUIFormatXMLPath); System.Console.WriteLine("Windows loaded"); return myGUI; } Here this line: System.Console.WriteLine("Image loaded? " + (GUIWindow.StandardBackgroundImage.ImageStrip != null)); Prints "true". To load the GUIWindows I need an "empty" constructor, which looks like that: public GUIWindow() { Name = ""; Buttons = new List<Button>(); ImagePath = ""; System.Console.WriteLine("Image loaded? (In win) " + (GUIWindow.StandardBackgroundImage.ImageStrip != null)); //Image = new IngameImage(StandardBackgroundImage); //System.Console.WriteLine( //Image.IsActive = false; SelectedButton = null; IsActive = false; } As you can see, I commented lines out in the constructor. Because: Otherwise this would crash. Here the line System.Console.WriteLine("Image loaded? (In win) " + (GUIWindow.StandardBackgroundImage.ImageStrip != null)); Doesn't print anything, it just crashes with the following errormessage: Building content threw NullReferenceException: Object reference not set to an object instance. Why does this happen? Before the program wants to load the List, it prints "true". But in the constructor, so in the loading of the list it prints "false". Can anybody please tell me why this happens and how to fix it?

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  • Replaceable parameter syntax meaning

    - by Alexander N.
    Replaceable parameter syntax for the console object in C#. I am taking the O'Reilly C# Course 1 and it is asking for a replaceable parameter syntax and it is not very clear on what that means. Currently I used this: double trouble = 99999.0009; double bubble = 11111.0001; Console.WriteLine(trouble * bubble); Am I missing the meaning of replaceable parameter syntax? Can someone provide an example for what I am looking for? Original question for the quiz: "Create two variables, both doubles, assign them numbers greater than 10,000, and include a decimal component. Output the result of multiplying the numbers together, but use replaceable parameter syntax of the Console object, and multiply the numbers within the call to the Console.WriteLine() method."

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  • Extremely slow login after upgrade from 11.10 to 12.04

    - by ocalex86
    I just upgraded my xubuntu 11.10 to 12.04 and now, when I login into the GUI, I have to wait about 3 minutes before the desktop appears. Only the background image is displayed. The login into the console works fine (with ctrl+alt+f2) Even stranger: If I login first in the console and then in the GUI, it boots quickly. If I login first in the GUI, switch to console and login, it takes 3 minutes to boot in the GUI. My machine is a thinkpad T420s.

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