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  • Explicit return form a Ruby method - implementation hiding, reuse and optimisations.

    - by Chris McCauley
    Hi, Rather than allowing a Ruby method to blindly return the last statement evaluated, is there any advantage to returning nil explicitly? In terms of implementation hiding and reuse, it seems dangerous to blindly allow the last expression evaluated to be returned - isn't there a danger that a user will rely on this only to get a nasty surprise when the implementation is modified? Surely returning nil would be better unless an explicit return value was given. Following on, is there an optimisation that Ruby can make when the return is a simple type rather than a reference to a more complex object? Chris

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  • Does ActiveRecord make Ruby on Rails code hard to test?

    - by Erik Öjebo
    I've spent most of my time in statically typed languages (primarily C#). I have some bad experiences with the Active Record pattern and unit testing, because of the static methods and the mix of entities and data access code. Since the Ruby community probably is the most test driven of the communities out there, and the Rails ActiveRecord seems popular, there must be some way of combining TDD and ActiveRecord based code in Ruby on Rails. I would guess that the problem goes away in dynamic languages, somehow, but I don't see how. So, what's the trick?

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  • Beginner - C# iteration through directory to produce a file list

    - by dassouki
    The end goal is to have some form of a data structure that stores a hierarchal structure of a directory to be stored in a txt file. I'm using the following code and so far, and I'm struggling with combining dirs, subdirs, and files. /// <summary> /// code based on http://msdn.microsoft.com/en-us/library/bb513869.aspx /// </summary> /// <param name="strFolder"></param> public static void TraverseTree ( string strFolder ) { // Data structure to hold names of subfolders to be // examined for files. Stack<string> dirs = new Stack<string>( 20 ); if ( !System.IO.Directory.Exists( strFolder ) ) { throw new ArgumentException(); } dirs.Push( strFolder ); while ( dirs.Count > 0 ) { string currentDir = dirs.Pop(); string[] subDirs; try { subDirs = System.IO.Directory.GetDirectories( currentDir ); } catch ( UnauthorizedAccessException e ) { MessageBox.Show( "Error: " + e.Message ); continue; } catch ( System.IO.DirectoryNotFoundException e ) { MessageBox.Show( "Error: " + e.Message ); continue; } string[] files = null; try { files = System.IO.Directory.GetFiles( currentDir ); } catch ( UnauthorizedAccessException e ) { MessageBox.Show( "Error: " + e.Message ); continue; } catch ( System.IO.DirectoryNotFoundException e ) { MessageBox.Show( "Error: " + e.Message ); continue; } // Perform the required action on each file here. // Modify this block to perform your required task. /* foreach ( string file in files ) { try { // Perform whatever action is required in your scenario. System.IO.FileInfo fi = new System.IO.FileInfo( file ); Console.WriteLine( "{0}: {1}, {2}", fi.Name, fi.Length, fi.CreationTime ); } catch ( System.IO.FileNotFoundException e ) { // If file was deleted by a separate application // or thread since the call to TraverseTree() // then just continue. MessageBox.Show( "Error: " + e.Message ); continue; } } */ // Push the subdirectories onto the stack for traversal. // This could also be done before handing the files. foreach ( string str in subDirs ) dirs.Push( str ); foreach ( string str in files ) MessageBox.Show( str ); }

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  • c# beginner problem

    - by Yehonatan
    I am trying to learning C# and I have problem with following code using System; class IfSelect { public static void Main() { string myInput; int myInt; Console.Write("Please enter a number: "); myInput = Console.ReadLine(); myInt = Int32.Parse(myInput); if (myInt = 10) { Console.WriteLine("Your number is 10.", myInt); } } }

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  • Beginner SQL question: querying gold and silver tag badges in Stack Exchange Data Explorer

    - by polygenelubricants
    I'm using the Stack Exchange Data Explorer to learn SQL, but I think the fundamentals of the question is applicable to other databases. I'm trying to query the Badges table, which according to Stexdex (that's what I'm going to call it from now on) has the following schema: Badges Id UserId Name Date This works well for badges like [Epic] and [Legendary] which have unique names, but the silver and gold tag-specific badges seems to be mixed in together by having the same exact name. Here's an example query I wrote for [mysql] tag: SELECT UserId as [User Link], Date FROM Badges Where Name = 'mysql' Order By Date ASC The (slightly annotated) output is: as seen on stexdex: User Link Date --------------- ------------------- // all for silver except where noted Bill Karwin 2009-02-20 11:00:25 Quassnoi 2009-06-01 10:00:16 Greg 2009-10-22 10:00:25 Quassnoi 2009-10-31 10:00:24 // for gold Bill Karwin 2009-11-23 11:00:30 // for gold cletus 2010-01-01 11:00:23 OMG Ponies 2010-01-03 11:00:48 Pascal MARTIN 2010-02-17 11:00:29 Mark Byers 2010-04-07 10:00:35 Daniel Vassallo 2010-05-14 10:00:38 This is consistent with the current list of silver and gold earners at the moment of this writing, but to speak in more timeless terms, as of the end of May 2010 only 2 users have earned the gold [mysql] tag: Quassnoi and Bill Karwin, as evidenced in the above result by their names being the only ones that appear twice. So this is the way I understand it: The first time an Id appears (in chronological order) is for the silver badge The second time is for the gold Now, the above result mixes the silver and gold entries together. My questions are: Is this a typical design, or are there much friendlier schema/normalization/whatever you call it? In the current design, how would you query the silver and gold badges separately? GROUP BY Id and picking the min/max or first/second by the Date somehow? How can you write a query that lists all the silver badges first then all the gold badges next? Imagine also that the "real" query may be more complicated, i.e. not just listing by date. How would you write it so that it doesn't have too many repetition between the silver and gold subqueries? Is it perhaps more typical to do two totally separate queries instead? What is this idiom called? A row "partitioning" query to put them into "buckets" or something?

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  • Beginner python - stuck in a loop

    - by Jeremy
    I have two begininer programs, both using the 'while' function, one works correctly, and the other gets me stuck in a loop. The first program is this; num=54 bob = True print('The guess a number Game!') while bob == True: guess = int(input('What is your guess? ')) if guess==num: print('wow! You\'re awesome!') print('but don\'t worry, you still suck') bob = False elif guess>num: print('try a lower number') else: print('close, but too low') print('game over')`` and it gives the predictable output of; The guess a number Game! What is your guess? 12 close, but too low What is your guess? 56 try a lower number What is your guess? 54 wow! You're awesome! but don't worry, you still suck game over However, I also have this program, which doesn't work; #define vars a = int(input('Please insert a number: ')) b = int(input('Please insert a second number: ')) #try a function def func_tim(a,b): bob = True while bob == True: if a == b: print('nice and equal') bob = False elif b > a: print('b is picking on a!') else: print('a is picking on b!') #call a function func_tim(a,b) Which outputs; Please insert a number: 12 Please insert a second number: 14 b is picking on a! b is picking on a! b is picking on a! ...(repeat in a loop).... Can someone please let me know why these programs are different? Thank you!

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  • jQuery simplifying code (beginner)

    - by Jonny Wood
    I'm getting to grips with jQuery but find myself repeating code over and over again... Surely there's a simpler way to write this: $('#more-mcr, #more-hilton, #more-lpool').hide(); $('#mcr-hatters').hoverIntent(function() { $('#mcr-hilton').stop().animate({opacity: 0.4}); $('#more-mcr').fadeIn({duration:200}); }, function() { $('#mcr-hilton').stop().animate({opacity: 1}); $('#more-mcr').fadeOut({duration:200}); }); $('#mcr-hilton').hoverIntent(function() { $('#mcr-hatters').stop().animate({opacity: 0.4}); $('#more-hilton').fadeIn({duration:200}); }, function() { $('#mcr-hatters').stop().animate({opacity: 1}); $('#more-hilton').fadeOut({duration:200}); }); $('#lpool-hostel').hoverIntent(function() { $('#more-lpool').fadeIn({duration:200}); }, function() { $('#more-lpool').fadeOut({duration:200}); }); $('#offers-mcr').hoverIntent(function() { $('#offers-lpool').stop().animate({opacity: 0.4}); $('#offers-bham').stop().animate({opacity: 0.4}); }, function() { $('#offers-lpool').stop().animate({opacity: 1}); $('#offers-bham').stop().animate({opacity: 1}); }); $('#offers-lpool').hoverIntent(function() { $('#offers-mcr').stop().animate({opacity: 0.4}); $('#offers-bham').stop().animate({opacity: 0.4}); }, function() { $('#offers-mcr').stop().animate({opacity: 1}); $('#offers-bham').stop().animate({opacity: 1}); }); $('#offers-bham').hoverIntent(function() { $('#offers-lpool').stop().animate({opacity: 0.4}); $('#offers-mcr').stop().animate({opacity: 0.4}); }, function() { $('#offers-lpool').stop().animate({opacity: 1}); $('#offers-mcr').stop().animate({opacity: 1}); }); I'd also like to set the delay for hoverIntent but I don't think this is possible with the way I've written the code currently...?

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  • C++ Beginner - Trouble using classes inside of classes

    - by Francisco P.
    Hello, I am working on a college project, where I have to implement a simple Scrabble game. I have a player class (containing a Score and the player's hand, in the form of a std::string, and a score class (containing a name and numeric (int) score). One of Player's member-functions is Score getScore(), which returns a Score object for that player. However, I get the following error on compile time: player.h(27) : error C2146: syntax error : missing ';' before identifier 'getScore' player.h(27) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int player.h(27) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int player.h(27) : warning C4183: 'getScore': missing return type; assumed to be a member function returning 'int' player.h(35) : error C2146: syntax error : missing ';' before identifier '_score' player.h(35) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int player.h(35) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int Here's lines 27 and 35, respectively: Score getScore(); //defined as public (...) Score _score; //defined as private I get that the compiler is having trouble recognizing Score as a valid type... But why? I have correctly included Score.h at the beginning of player.h: #include "Score.h" #include "Deck.h" #include <string> I have a default constructor for Score defined in Score.h: Score(); //score.h //score.cpp Score::Score() { _name = ""; _points = 0; } Any input would be appreciated! Thanks for your time, Francisco EDIT: As requested, score.h and player.h: http://pastebin.com/3JzXP36i http://pastebin.com/y7sGVZ4A

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  • Beginner SQL question: arithmetic with multiple COUNT(*) results

    - by polygenelubricants
    Continuing with the spirit of using the Stack Exchange Data Explorer to learn SQL, (see: Can we become our own “Northwind” for teaching SQL / databases?), I've decided to try to write a query to answer a simple question (on meta): What % of stackoverflow users have over 10,000 rep?. Here's what I've done: Query#1 SELECT COUNT(*) FROM Users WHERE Users.Reputation >= 10000 Result: 556 Query#2 SELECT COUNT(*) FROM USERS Result: 227691 Now, how do I put them together into one query? What is this query idiom called? What do I need to write so I can get, say, a one-row three-column result like this: 556 227691 0,00244190592

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  • Simplest possible rack app -> permission error

    - by 7stud
    Here's the program(1.rb) blah blah blah blah blah blah: require 'rack' my_rack = lambda { |env| [200, {}, ["Hello. The time is: #{Time.now}"]] } handler = Rack::Handler::WEBrick handler.run(my_rack, :PORT => 12_500) Here's the error (blah blah blah blah blah): ~/ruby_programs$ ruby 1.rb [2012-12-07 21:49:09] INFO WEBrick 1.3.1 [2012-12-07 21:49:09] INFO ruby 1.9.3 (2012-04-20) [x86_64-darwin10.8.0] [2012-12-07 21:49:09] WARN TCPServer Error: Permission denied - bind(2) [2012-12-07 21:49:09] WARN TCPServer Error: Permission denied - bind(2) /Users/7stud/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/utils.rb:85:in `initialize': Permission denied - bind(2) (Errno::EACCES) from /Users/7stud/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/utils.rb:85:in `new' from /Users/7stud/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/utils.rb:85:in `block in create_listeners' from /Users/7stud/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/utils.rb:82:in `each' from /Users/7stud/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/utils.rb:82:in `create_listeners' from /Users/7stud/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/server.rb:82:in `listen' from /Users/7stud/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/server.rb:70:in `initialize' from /Users/7stud/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/httpserver.rb:45:in `initialize' from /Users/7stud/.rvm/gems/ruby-1.9.3-p194@programming/gems/rack-1.4.1/lib/rack/handler/webrick.rb:10:in `new' from /Users/7stud/.rvm/gems/ruby-1.9.3-p194@programming/gems/rack-1.4.1/lib/rack/handler/webrick.rb:10:in `run' from 1.rb:5:in `<main>' ~/ruby_programs$ Here's line 85 of ../webrick/utils.rb: sock = TCPServer.new(ai[3], port) If I replace the code in 1.rb with this: require 'socket' server = TCPServer.new 12_000 # Server bind to port 2000 loop do client = server.accept # Wait for a client to connect client.puts "Hello !" client.puts "Time is #{Time.now}" client.close end I don't get any errors, and if I enter the address: http://localhost:12000/ in my browser, I get the expected output: Hello ! Time is 2012-12-07 18:58:15 -0700

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  • recommended parser for XML in java(absolute beginner to xml)

    - by poeschlorn
    Hi Pro's, which parser (java) would you recommend for parsing GPX data? Im looking for a one that is very intuitive to use and should not need too much RAM (it seems that DOM requires too much, doesn't it?). I have no idea about parsing xml, so it is time for me to learn this ;-) My documents are not very huge and are always read twice(a point for DOM), but I don't want to keep as few things as possible in RAM. What would you do in this situation? Which one would you coose and why?

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  • Beginner question: What is binding?

    - by JDelage
    Hi, I was trying to understand the difference between early and late binding, and in the process realized that the concept of binding is nebulous to me. I think I understand that it relates to the way data-as-a-word-of-memory is linked to type-as-a-set-of-language-features but I am not sure those are the right concepts. Also, how does understanding this deeply help people become better programmers? Please note: This question is not "what is late v. early binding" or "what are the trade-offs between the 2". Those already exist here. Thanks, JDelage

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  • Android beginner

    - by Karthick
    Hi I am new android. I need to know how to install it in windows xp and which one is the best IDE and what are the requirements are needed. And I need to know how to develop an application in that platform.

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  • Beginner having a problem with classes

    - by David
    I'm working through O'Reilly's "Learning Python" and having a problem with classes. I think I understand the concept, but in practice have stumbled upon this problem. Fron page 88-89: >>> class Worker: def __innit__(self, name, pay): self.name=name self.pay=pay def lastName(self): return self.name.split()[-1] def giveRaise(self, percent): self.pay*=(1.0+percent) Then the book says "Calling the class like a function generates instances of a new type ...etc" and gives this example. bob = Worker('Bob Smith', 50000) This gives me this error: TypeError: this constructor takes no arguments. And then I start muttering profanities. So what am I doing wrong here? Thanks for the help.

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  • good beginner tutorial for turbogears 2

    - by coder10
    I find myself struggling to do simple things that would normally take me about 5 minutes to do in PHP. At the moment, I'm trying to create a basic form which will print the details on another page when you click submit. Looking at the documentation, I find examples but none explaining why it works in such a way.

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  • doubt about radio button mysql php beginner

    - by Marcelo
    Hi, i'm an engineering student and i'm developing a simple software based on html,php and mysql. I learned this topics on w3schools, i know only the basics. I tired to search about this in this website but I thought the doubts about php,mysql, radio buttons but they were much more complex than I need, and that i could understand. Sorry for the english. (Q1)Ex: $email=$_REQUEST['email'] , in this case the input is text, if it where like a radio button for ex: sex: male or female, how would it be? (Q2) what would be the type of this field (for exemple sex in question 1) in the database: text, int, varchar ? thanks for the attention

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  • Python beginner confused by a complex line of code

    - by Protean
    I understand the gist of the code, that it forms permutations; however, I was wondering if someone could explain exactly what is going on in the return statement. def perm(l): sz = len(l) print (l) if sz <= 1: print ('sz <= 1') return [l] return [p[:i]+[l[0]]+p[i:] for i in range(sz) for p in perm(l[1:])]

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  • Python beginner, strange output problem

    - by Protean
    I'm having a weird problem with the following piece of code. from math import sqrt def Permute(array): result1 = [] result2 = [] if len(array) <= 1: return array for subarray in Permute(array[1:]): for i in range(len(array)): temp1 = subarray[:i]+array[0]+subarray[i:] temp2 = [0] for num in range(len(array)-1): temp2[0] += (sqrt(pow((temp1[num+1][1][0]-temp1[num][1][0]),2) + pow((temp1[num+1][1][1]-temp1[num][1][1]),2))) result1.append(temp1+temp2) return result1 a = [['A',[50,1]]] b = [['B',[1,1]]] c = [['C',[100,1]]] array = [a,b,c] result1 = Permute(array) for i in range(len(result1)): print (result1[i]) print (len(result1)) What it does is find all the permutations of the points abc and then returns them along with the sum of the distances between each ordered point. It does this; however, it also seems to report a strange additional value, 99. I figure that the 99 is coming from the computation of the distance between point a and c but I don't understand why it is appearing in the final output as it does.

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  • Beginner: Restore previously serialized JFrame-object, how?

    - by elementz
    Hi all. I have managed to serialize my very basic GUI-object containing a JTextArea and a few buttons to a file 'test.ser'. Now, I would like to completely restore the previously saved state from 'test.ser', but seem to have a misconception of how to properly deserialize an objects state. The class MyFrame creates the JFrame and serializes it. Now I tried to deserialize like so: public class Deserialize { static Deserialize ds; MyFrame frame; public static void main(String[] args) { try { ds.deserialize(); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public void deserialize() throws ClassNotFoundException { try { ObjectInputStream ois = new ObjectInputStream(new FileInputStream("test.ser")); frame = (MyFrame) ois.readObject(); ois.close(); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } Maybe somebody could point me into the direction where my misconception is? Thx in advance!

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  • Validating Age field javascript beginner

    - by Marcelo
    Hi people, I'm trying to validate an age field in a form but I'm having some problem. First I tried to make sure that the field will not be send empty. I don't know javascript so I searched some scripts and adapted them to this: function isInteger (s) { var i; if (isEmpty(s)) if (isInteger.arguments.length == 1) return 0; else return (isInteger.arguments[1] == true); for (i = 0; i < s.length; i++) { var c = s.charAt(i); if (!isDigit(c)) return false; } return true; } function isEmpty(s) { return ((s == null) || (s.length == 0)) } function validate_required(field,alerttxt) { with (field) { if (value==null||value=="") { alert(alerttxt);return false; } else { return true; } } } function validate_form(thisform) { with (thisform) { if ((validate_required(age,"Age must be filled out!")==false) || isInteger(age,"Age must be and int number")==false)) {email.focus();return false;} } } //html part <form action="doador.php" onsubmit="return validate_form(this)" method="post"> It's working fine for empty fields, but if I type any letters or characters in age field, it'll be sent and saved a 0 in my database. Can any one help me ? Sorry for any mistake in English, and thanks in andvance for your help.

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  • Beginner Java Question about Integer.parseInt() and casting

    - by happysoul
    so when casting like in the statement below :- int randomNumber=(int) (Math.random()*5) it causes the random no. generated to get converted into an int.. Also there's this method I just came across Integer.parseInt() which does the same ! i.e return an integer Why two different ways to make a value an int ? Also I made a search and it says parseInt() takes string as an argument.. So does this mean that parseInt() is ONLY to convert String into integer ? What about this casting then (int) ?? Can we use this to convert a string to an int too ? sorry if it sounds like a dumb question..I am just confused and trying to understand Help ?

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