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  • Do bit operations cause programs to run slower?

    - by flashnik
    I'm dealing with a problem which needs to work with a lot of data. Currently its values are represented as an unsigned int. I know that real values do not exceed a limit of 1000. Questions I can use unsigned short to store it. An upside to this is that it'll use less storage space to store the value. Will performance suffer? If I decided to store data as short but all the calling functions use int, it's recognized that I need to convert between these datatypes when storing or extracting values. Will performance suffer? Will the loss in performance be dramatic? If I decided to not use short but just 10 bits packed into an array of unsigned int. What will happen in this case comparing with previous ones?

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  • Setting last N bits in an array

    - by Martin
    I'm sure this is fairly simple, however I have a major mental block on it, so I need a little help here! I have an array of 5 integers, the array is already filled with some data. I want to set the last N bits of the array to be random noise. [int][int][int][int][int] set last 40 bits [unchanged][unchanged][unchanged][24 bits of old data followed 8 bits of randomness][all random] This is largely language agnostic, but I'm working in C# so bonus points for answers in C#

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  • A simple string array Iteration in C# .NET doesn't work

    - by met.lord
    This is a simple code that should return true or false after comparing each element in a String array with a Session Variable. The thing is that even when the string array named 'plans' gets the right attributes, inside the foreach it keeps iterating only over the first element, so if the Session Variable matches other element different than the first one in the array it never returns true... You could say the problem is right there in the foreach cicle, but I cant see it... I've done this like a hundred times and I can't understand what am I doing wrong... Thank you protected bool ValidatePlans() { bool authorized = false; if (RequiredPlans.Length > 0) { string[] plans = RequiredPlans.Split(','); foreach (string plan in plans) { if (MySessionInfo.Plan == plan) authorized = true; } } return authorized; }

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  • Why does the output look like this?

    - by cjk
    I have a c program below, I would like to send out a 32 bit message in a particular order Eg.0x00000001. #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <stdint.h> struct test { uint16_t a; uint16_t b; }; int main(int argc, char const *argv[]) { char buf[4]; struct test* ptr=(struct test*)buf; ptr->a=0x0000; ptr->b=0x0001; printf("%x %x\n",buf[0],buf[1]); //output is 0 0 printf("%x %x\n",buf[2],buf[3]); //output is 1 0 return 0; } Then I test it by print out the values in char array. I got output in the above comments. Shouldn't the output be 0 0 and 0 1? since but[3] is the last byte? Is there anything I missed? Thanks!

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  • ToList()-- Does it Create a New List?

    - by Ngu Soon Hui
    Let's say I have a class public class MyObject { public int SimpleInt{get;set;} } And I have a List<MyObject>, and I ToList() it and then change one of the SimpleInt, will my change be propagated back to the original list. In other words, what would be the output of the following method? public void RunChangeList() { var objs = new List<MyObject>(){new MyObject(){SimpleInt=0}}; var whatInt = ChangeToList(objs ); } public int ChangeToList(List<MyObject> objects) { var objectList = objects.ToList(); objectList[0].SimpleInt=5; return objects[0].SimpleInt; } Why? P/S: I'm sorry if it seems obvious to find out. But I don't have compiler with me now...

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  • Split string var

    - by lidermin
    Hi, I have a question: Let's say I have this string var: string strData = "1|2|3|4||a|b|c|d" Then, I make a Split: strNumbers[] = strData.Split("||"); //something like this, I know It's not this simple I need two separate parts, each one containing this: //strNumbers -> {"1","2","3","4"},{"a","b","c","d"} So that after that, I could do this: string[] strNumArray[] = strNumbers[0].Split('|'); //strNumArray -> '1', '2', '3', '4' And same with the other part (letters). Is it possible? to make this double split with the same character, but the first time the character is repeated twice?. Thanks. PD. I'm using C#.

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  • java phone number validation....

    - by user69514
    Here is my problem: Create a constructor for a telephone number given a string in the form xxx-xxx-xxxx or xxx-xxxx for a local number. Throw an exception if the format is not valid. So I was thinking to validate it using a regular expression, but I don't know if I'm doing it correctly. Also what kind of exception would I have to throw? Do I need to create my own exception? public TelephoneNumber(String aString){ if(isPhoneNumberValid(aString)==true){ StringTokenizer tokens = new StringTokenizer("-"); if(tokens.countTokens()==3){ areaCode = Integer.parseInt(tokens.nextToken()); exchangeCode = Integer.parseInt(tokens.nextToken()); number = Integer.parseInt(tokens.nextToken()); } else if(tokens.countTokens()==2){ exchangeCode = Integer.parseInt(tokens.nextToken()); number = Integer.parseInt(tokens.nextToken()); } else{ //throw an excemption here } } } public static boolean isPhoneNumberValid(String phoneNumber){ boolean isValid = false; //Initialize reg ex for phone number. String expression = "(\\d{3})(\\[-])(\\d{4})$"; CharSequence inputStr = phoneNumber; Pattern pattern = Pattern.compile(expression); Matcher matcher = pattern.matcher(inputStr); if(matcher.matches()){ isValid = true; } return isValid; } Hi sorry, yes this is homework. For this assignments the only valid format are xxx-xxx-xxxx and xxx-xxxx, all other formats (xxx)xxx-xxxx or xxxxxxxxxx are invalid in this case. I would like to know if my regular expression is correct

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  • Statically checking a Java app for link errors

    - by monorailkitty
    I have a scenario where I have code written against version 1 of a library but I want to ship version 2 of the library instead. The code has shipped and is therefore not changeable. I'm concerned that it might try to access classes or members of the library that existed in v1 but have been removed in v2. I figured it would be possible to write a tool to do a simple check to see if the code will link against the newer version of the library. I appreciate that the code may still be very broken even if the code links. I am thinking about this from the other side - if the code won't link then I can be sure there is a problem. As far as I can see, I need to run through the bytecode checking for references, method calls and field accesses to library classes then use reflection to check whether the class/member exists. I have three-fold question: (1) Does such a tool exist already? (2) I have a niggling feeling it is much more complicated that I imagine and that I have missed something major - is that the case? (3) Do you know of a handy library that would allow me to inspect the bytecode such that I can find the method calls, references etc.? Thanks!

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  • C++ exam question on string class implementation

    - by Carlucho
    I just took an exam where i was asked the following: Write the function body of each of the methods GenStrLen, InsertChar and StrReverse for the given code bellow. You must take into consideration the following; How strings are constructed in C++ The string must not overflow Insertion of character increases its length by 1 An empty string is indicated by StrLen = 0 class Strings { private: char str[80]; int StrLen; public: // Constructor Strings() { StrLen=0; }; // A function for returning the length of the string 'str' int GetStrLen(void) { }; // A function to inser a character 'ch' at the end of the string 'str' void InsertChar(char ch) { }; // A function to reverse the content of the string 'str' void StrReverse(void) { }; }; The answer I gave was something like this (see bellow). My one of problem is that used many extra variables and that makes me believe am not doing it the best possible way, and the other thing is that is not working.... class Strings { private: char str[80]; int StrLen; int index; // *** Had to add this *** public: Strings(){ StrLen=0; } int GetStrLen(void){ for (int i=0 ; str[i]!='\0' ; i++) index++; return index; // *** Here am getting a weird value, something like 1829584505306 *** } void InsertChar(char ch){ str[index] = ch; // *** Not sure if this is correct cuz I was not given int index *** } void StrRevrse(void){ GetStrLen(); char revStr[index+1]; for (int i=0 ; str[i]!='\0' ; i++){ for (int r=index ; r>0 ; r--) revStr[r] = str[i]; } } }; I would appreciate if anyone could explain me toughly what is the best way to have answered the question and why. Also how come my professor closes each class function like " }; " i thought that was only used for ending classes and constructors only. Thanks a lot for your help.

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  • How to manually (bitwise) perform (float)x? (homework)

    - by Silver
    Now, here is the function header of the function I'm supposed to implement: /* * float_from_int - Return bit-level equivalent of expression (float) x * Result is returned as unsigned int, but * it is to be interpreted as the bit-level representation of a * single-precision floating point values. * Legal ops: Any integer/unsigned operations incl. ||, &&. also if, while * Max ops: 30 * Rating: 4 */ unsigned float_from_int(int x) { ... } We aren't allowed to do float operations, or any kind of casting. Now I tried to implement the first algorithm given at this site: http://locklessinc.com/articles/i2f/ Here's my code: unsigned float_from_int(int x) { // grab sign bit int xIsNegative = 0; int absValOfX = x; if(x < 0){ xIsNegative = 1; absValOfX = -x; } // zero case if(x == 0){ return 0; } //int shiftsNeeded = 0; /*while(){ shiftsNeeded++; }*/ unsigned I2F_MAX_BITS = 15; unsigned I2F_MAX_INPUT = ((1 << I2F_MAX_BITS) - 1); unsigned I2F_SHIFT = (24 - I2F_MAX_BITS); unsigned result, i, exponent, fraction; if ((absValOfX & I2F_MAX_INPUT) == 0) result = 0; else { exponent = 126 + I2F_MAX_BITS; fraction = (absValOfX & I2F_MAX_INPUT) << I2F_SHIFT; i = 0; while(i < I2F_MAX_BITS) { if (fraction & 0x800000) break; else { fraction = fraction << 1; exponent = exponent - 1; } i++; } result = (xIsNegative << 31) | exponent << 23 | (fraction & 0x7fffff); } return result; } But it didn't work (see test error below): Test float_from_int(-2147483648[0x80000000]) failed... ...Gives 0[0x0]. Should be -822083584[0xcf000000] 4 4 0 float_times_four I don't know where to go from here. How should I go about parsing the float from this int?

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  • Remove special chars from URL

    - by John Jones
    Hi, I have a product database and I am displaying trying to display them as clean URLs, below is example product names: PAUL MITCHELL FOAMING POMADE (150ml) American Crew Classic Gents Pomade 85g Tigi Catwalk Texturizing Pomade 50ml What I need to do is display like below in the URL structrue: www.example.com/products/paul-mitchell-foaming-gel(150ml) The problem I have is I want to do the following: Remove anything with braquets(and the braquets) Remove any numbers next to g or ml e.g. 400ml, 10g etc... I have been banging my head trying different string replaces but cant get it right, I would really appreciate some help. Cheers

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  • Remove leading zero's from alphanumeic text

    - by cedar715
    I've seen questions to prefix zeros here in SO. But not the other way !! Can you guys suggest me how to remove the leading zeros in alphanumeric text. Are there any built-in APIs or do I need to write a method to trim the leading zero's? Example: 01234 converts to 1234 0001234a converts to 1234a 001234-a converts to 1234-a 101234 remains as 101234 2509398 remains as 2509398 123z remains as 123z 000002829839 converts to 2829839

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  • How to invert alternate bits of a number

    - by Cupidvogel
    The problem is how to invert alternate bits of a number, starting from the LSB. Currently what I am doing is first doing a count = -1 while n: n >>= 1 count += 1 to first find the position of the leftmost set bit, then running a loop to invert every alternate bit: i = 0 while i <= count: num ^= 1<<i i += 2 Is there a quick hack solution instead of this rather boring loop solution? Of course, the solution can't make any asumption about the size of the integer.

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  • BufferedImage & ColorModel in Java

    - by spol
    I am using a image processing library in java to manipulate images.The first step I do is I read an image and create a java.awt.Image.BufferedImage object. I do it in this way, BufferedImage sourceImage = ImageIO.read( new File( filePath ) ); The above code creates a BufferedImage ojbect with a DirectColorModel: rmask=ff0000 gmask=ff00 bmask=ff amask=0. This is what happens when I run the above code on my macbook. But when I run this same code on a linux machine (hosted server), this creates a BufferedImage object with ColorModel: #pixelBits = 24 numComponents = 3 color space = java.awt.color.ICC_ColorSpace@c39a20 transparency = 1 has alpha = false isAlphaPre = false. And I use the same jpg image in both the cases. I don't know why the color model on the same image is different when run on mac and linux. The colormodel for mac has 4 components and the colormodel for linux has 3 components.There is a problem arising because of this, the image processing library that I use always assumes that there are always 4 components in the colormodel of the image passed, and it throws array out of bounds exception when run on linux box. But on macbook, it runs fine. I am not sure if I am doing something wrong or there is a problem with the library. Please let me know your thoughts. Also ask me any questions if I am not making sense!

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  • GDI+, using DrawImage to draw a transperancy mask of the source image

    - by sold
    Is it possible to draw a transperancy mask of an image (that is, paint all visible pixels with a constant color) using Graphics::DrawImage? I am not looking for manually scanning the image pixel-by-pixel and creating a seperate mask image, I wonder if it's possible to draw one directly from the original image. My guessing is that it should be done with certain manipulations to ImageAttributes, if possible at all. The color of the mask is arbitrary and should be accurate, and it would be a plus if there can be a threshold value for the transparency.

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  • C# type safe and developer friendly list/collection technique

    - by Agile Noob
    I am populating a "Dictionary" with the results of an sp call. The key is the field name and the value is whatever value the sp returns for the field. This is all well and good but I'd like developers to have a predefined list of keys to access this list, for safety and documentation reasons. What I'd like to do is have something like an enum as a key for the dictionary so developers can safely access the list, but still have the ability to access the dictionary with a string key value. I am hoping to have a list of string values that I can access with an enum key AND a string key. Please make sure any suggestions are simple to implement, this is not the kind of thing I'm willing to build a lot of overhead to implement.

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  • parse this directory path without losing slash

    - by PPTim
    hi, I have a wxPython application. I am taking in a directory path from a textbox using GetValue(). I notice that while trying to parse in the directory path "C:\Documents and Settings\UserName\Desktop\InputFile.xls", python sees the string as 'C:\\Documents and Settings\UserName\\Desktop\\InputFile.xls' (missing a slash between "Settings" and "UserName). Why is it that only that slash is not correctly escaped? Once the string has been changed to 'C:\Documents and Settings\UserName\Desktop\InputFile.xls', is there a type conversion or function that can does this properly? Thanks.

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  • List<string> doesn't update the UI when change occurs [WPF]

    - by Hard Turner
    <ListBox x:Name="MainList" HorizontalAlignment="Left" Height="468" Margin="10,10,0,0" VerticalAlignment="Top" Width="100" ItemsSource="{Binding Items,Mode=TwoWay}" DisplayMemberPath="Name"/> [Serializable()] public class MYcontainer : INotifyPropertyChanged,ISerializable { private List<MYClass> _items = new List<MYClass>(); public List<MYClass> Items { get{ return _items;} set { this._items =value; OnPropertyChanged("Items"); } public event PropertyChangedEventHandler PropertyChanged; public void OnPropertyChanged(string propertyName = null) { var eventHandler = this.PropertyChanged; if (eventHandler != null) eventHandler(this, new PropertyChangedEventArgs(propertyName)); } } when i add an item to "Items" the UI doesnt update, the binding is working fine, since if i closed the window and opened it again, the new items appear correctly what am i doing wrong? i know if i used observablecollection it will work fine, but shouldn't it work with List<? , i already have in another window a string[] property and it update fine

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  • I need to pad IP addresses with Zeroes for each octet

    - by Felipe Alvarez
    Starting with a string of an unspecified length, I need to make it exactly 43 characters long (front-padded with zeroes). It is going to contain IP addresses and port numbers. Something like: ### BEFORE # Unfortunately includes ':' colon 66.35.205.123.80-137.30.123.78.52172: ### AFTER # Colon removed. # Digits padded to three (3) and five (5) # characters (for IP address and port numbers, respectively) 066.035.05.123.00080-137.030.123.078.52172 This is similar to the output produced by tcpflow. Programming in Bash. I can provide copy of script if required. If it's at all possible, it would be nice to use a bash built-in, for speed. Is printf suitable for this type of thing?

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  • when to use StringBuilder in java

    - by kostja
    It is supposed to be generally preferable to use a StringBuilder for String concatenation in Java. Is it always the case? What i mean is : Is the overhead of creating a StringBuilder object, calling the append() method and finally toString() smaller then concatenating existing Strings with + for 2 Strings already or is it only advisable for more Strings? If there is such a threshold, what does it depend on (the String length i suppose, but in which way)? And finally - would you trade the readability and conciseness of the + concatenation for the performance of the StringBuilder in smaller cases like 2, 3, 4 Strings?

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