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  • Naming member functions/methods with a single underscore, good style or bad?

    - by Extrakun
    In some languages where you cannot override the () operator, I have seen methods with a single underscore, usually for 'helper' classes. Something likes this: class D10 { public function _() { return rand(1,10); } } Is it better to have the function called Roll()? Is a underscore fine? After all, there is only one function, and it removes the need to look up the name of the class. Any thoughts?

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  • How can I refactor this JavaScript code to avoid making functions in a loop?

    - by Bungle
    I wrote the following code for a project that I'm working on: var clicky_tracking = [ ['related-searches', 'Related Searches'], ['related-stories', 'Related Stories'], ['more-videos', 'More Videos'], ['web-headlines', 'Publication'] ]; for (var x = 0, length_x = clicky_tracking.length; x < length_x; x++) { links = document.getElementById(clicky_tracking[x][0]) .getElementsByTagName('a'); for (var y = 0, length_y = links.length; y < length_y; y++) { links[y].onclick = (function(name, url) { return function() { clicky.log(url, name, 'outbound'); }; }(clicky_tracking[x][1], links[y].href)); } } What I'm trying to do is: define a two-dimensional array, with each instance the inner arrays containing two elements: an id attribute value (e.g., "related-searches") and a corresponding description (e.g., "Related Searches"); for each of the inner arrays, find the element in the document with the corresponding id attribute, and then gather a collection of all <a> elements (hyperlinks) within it; loop through that collection and attach an onclick handler to each hyperlink, which should call clicky.log, passing in as parameters the description that corresponds to the id (e.g., "Related Searches" for the id "related-searches") and the value of the href attribute for the <a> element that was clicked. Hopefully that wasn't thoroughly confusing! The code may be more self-explanatory than that. I believe that what I've implemented here is a closure, but JSLint complains: http://img.skitch.com/20100526-k1trfr6tpj64iamm8r4jf5rbru.png So, my questions are: How can I refactor this code to make JSLint agreeable? Or, better yet, is there a best-practices way to do this that I'm missing, regardless of what JSLint thinks? Should I rely on event delegation instead? That is, attaching onclick event handlers to the document elements with the id attributes in my arrays, and then looking at event.target? I've done that once before and understand the theory, but I'm very hazy on the details, and would appreciate some guidance on what that would look like - assuming this is a viable approach. Thanks very much for any help!

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  • A problem with assertRaises function in Python

    - by anton.k.
    Hello,guys! I am trying to run the following test self.assertRaises(Exception,lambda: unit_test.testBasic()) where test.testBasic() is class IsPrimeTest(unittest.TestCase): def assertRaises(self,exception,callable,*args,**kwargs): print('dfdf') temp = callable super().assertRaises(exception,temp,*args,**kwargs) def testBasic_helper(self): self.failIf(is_prime(2)) self.assertTrue(is_prime(1)) where prime is a function,and but in self.assertRaises(Exception,lambda: unit_test.testBasic()) the lambda function doesnt throws an exception after the test def testBasic_helper(self): self.failIf(is_prime(2)) self.assertTrue(is_prime(1)) fails Can somebody offers a solution to the problem?

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  • How do I call functions of an object inside the same object?

    - by Roly
    I have the following Javascript code add_num = { f: function(html, num) { alert(this.page); }, page : function() { return parseInt(this.gup('page')); }, gup : function(name) { name = name.replace(/[\[]/,'\\\[').replace(/[\]]/,'\\\]'); var regex = new RegExp('[\\?&]'+name+'=([^&#]*)'); var results = regex.exec(window.location.href); if(results == null) return ''; else return results[1]; } } But when I call add_num.f() what I get from alert() is the actual code of page. That is, it returns function() { return parseInt(this.gup('page')); } I was expecting a numeric value and not any code at all.

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  • JS: Why isn't this variable available to the other functions?

    - by Marius Jonsson
    Hello there, I've am trying to make a canvas animation: var context; var meter; var pin; function init() { var meter = new Image(); var pin = new Image(); var context = document.getElementById('canvas').getContext('2d'); meter.src = 'background.png'; pin.src = 'needle.png'; context.drawImage(meter,0,0); context.translate(275,297); context.save(); setTimeout(startup,500); } function startup() { var r=2; // set rpm here. var i=r*36-27; var angleInRadians = 3.14159265 * i/180; //converting degree to radian context.rotate(angleInRadians); //rotating by angle context.drawImage(pin,-250,-3); //adjusting pin center at meter center context.restore(); } You can see the script at http://www.kingoslo.com/instruments/ With firebug I get error saying that context is undefined, which I think is strange. Thanks. Kind regards, Marius

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  • iPhone Apps, Objective C, a Graph, and Functions vs. Objects (or something like that)

    - by BillEccles
    Gentleones, I've got a UIImageView that I have in a UIView. This particular UIImageView displays a PNG of a graph. It's important for this particular view controller and another view controller to know what the graph "looks like," i.e., the function described by the PNG graph. These other view controllers need to be able to call a "function" of some sort with the X value returning the Y value. Please ignore the fact (from an outsider's perspective) that I could probably generate the graph programmatically. So my questions are: 1 - Where should I put this function? Should it go in one view controller or the other, or should it go in its own class or main or...? 2 - Should it be an object in some way? Or should it be a straight function? (In either case, where's it belong?) Pardon the apparent n00b-iness of the question. It's 'cause I'm honestly a n00b! This OOP stuff is giving my head a spin having been a procedural programmer for 30 years. (And I choose to learn it by jumping into an iPhone app. Talk about baptism by fire!) Thanks in advance,Bill

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  • Is it bad practice to have a long initialization method?

    - by Paperflyer
    many people have argued about function size. They say that functions in general should be pretty short. Opinions vary from something like 15 lines to "about one screen", which today is probably about 40-80 lines. Also, functions should always fulfill one task only. However, there is one kind of function that frequently fails in both criteria in my code: initialization functions. For example in an audio application, the audio hardware/API has to be set up, audio data has to be converted to a suitable format and the object state has to properly initialized. These are clearly three different tasks and depending on the API this can easily span more than 50 lines. The thing with init-functions is that they are generally only called once, so there is no need to re-use any of the components. Would you still break them up into several smaller functions would you consider big initialization functions to be ok?

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  • Is it safe to assert a functions return type?

    - by wb
    This question is related to this question. I have several models stored in a collection. I loop through the collection and validate each field. Based on the input, a field can either be successful, have an error or a warning. Is it safe to unit test each decorator and assert that the type of object returned is what you would expect based on the given input? I could perhaps see this being an issue for a language with function return types since my validation function can return one of 3 types. This is the code I'm fiddling with: <!-- #include file = "../lib/Collection.asp" --> <style type="text/css"> td { padding: 4px; } td.error { background: #F00F00; } td.warning { background: #FC0; } </style> <% Class UserModel Private m_Name Private m_Age Private m_Height Public Property Let Name(value) m_Name = value End Property Public Property Get Name() Name = m_Name End Property Public Property Let Age(value) m_Age = value End Property Public Property Get Age() Age = m_Age End Property Public Property Let Height(value) m_Height = value End Property Public Property Get Height() Height = m_Height End Property End Class Class NameValidation Private m_Name Public Function Init(name) m_Name = name End Function Public Function Validate() Dim validationObject If Len(m_Name) < 5 Then Set validationObject = New ValidationError Else Set validationObject = New ValidationSuccess End If validationObject.CellValue = m_Name Set Validate = validationObject End Function End Class Class AgeValidation Private m_Age Public Function Init(age) m_Age = age End Function Public Function Validate() Dim validationObject If m_Age < 18 Then Set validationObject = New ValidationError ElseIf m_Age = 18 Then Set validationObject = New ValidationWarning Else Set validationObject = New ValidationSuccess End If validationObject.CellValue = m_Age Set Validate = validationObject End Function End Class Class HeightValidation Private m_Height Public Function Init(height) m_Height = height End Function Public Function Validate() Dim validationObject If m_Height > 400 Then Set validationObject = New ValidationError ElseIf m_Height = 324 Then Set validationObject = New ValidationWarning Else Set validationObject = New ValidationSuccess End If validationObject.CellValue = m_Height Set Validate = validationObject End Function End Class Class ValidationError Private m_CSSClass Private m_CellValue Public Property Get CSSClass() CSSClass = "error" End Property Public Property Let CellValue(value) m_CellValue = value End Property Public Property Get CellValue() CellValue = m_CellValue End Property End Class Class ValidationWarning Private m_CSSClass Private m_CellValue Public Property Get CSSClass() CSSClass = "warning" End Property Public Property Let CellValue(value) m_CellValue = value End Property Public Property Get CellValue() CellValue = m_CellValue End Property End Class Class ValidationSuccess Private m_CSSClass Private m_CellValue Public Property Get CSSClass() CSSClass = "" End Property Public Property Let CellValue(value) m_CellValue = value End Property Public Property Get CellValue() CellValue = m_CellValue End Property End Class Class ModelValidator Public Function ValidateModel(model) Dim modelValidation : Set modelValidation = New CollectionClass ' Validate name Dim name : Set name = New NameValidation name.Init model.Name modelValidation.Add name ' Validate age Dim age : Set age = New AgeValidation age.Init model.Age modelValidation.Add age ' Validate height Dim height : Set height = New HeightValidation height.Init model.Height modelValidation.Add height Dim validatedProperties : Set validatedProperties = New CollectionClass Dim modelVal For Each modelVal In modelValidation.Items() validatedProperties.Add modelVal.Validate() Next Set ValidateModel = validatedProperties End Function End Class Dim modelCollection : Set modelCollection = New CollectionClass Dim user1 : Set user1 = New UserModel user1.Name = "Mike" user1.Age = 12 user1.Height = 32 modelCollection.Add user1 Dim user2 : Set user2 = New UserModel user2.Name = "Phil" user2.Age = 18 user2.Height = 432 modelCollection.Add user2 Dim user3 : Set user3 = New UserModel user3.Name = "Michele" user3.Age = 32 user3.Height = 324 modelCollection.Add user3 ' Validate all models in the collection Dim modelValue Dim validatedModels : Set validatedModels = New CollectionClass For Each modelValue In modelCollection.Items() Dim objModelValidator : Set objModelValidator = New ModelValidator validatedModels.Add objModelValidator.ValidateModel(modelValue) Next %> <table> <tr> <td>Name</td> <td>Age</td> <td>Height</td> </tr> <% Dim r, c For Each r In validatedModels.Items() %><tr><% For Each c In r.Items() %><td class="<%= c.CSSClass %>"><%= c.CellValue %></td><% Next %></tr><% Next %> </table> Thank you.

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  • Is it undefined behavior in the case of the private functions call in the initializer list?

    - by Alexey Malistov
    Consider the following code: struct Calc { Calc(const Arg1 & arg1, const Arg2 & arg2, /* */ const ArgN & argn) : arg1(arg1), arg2(arg2), /* */ argn(argn), coef1(get_coef1()), coef2(get_coef2()) { } int Calc1(); int Calc2(); int Calc3(); private: const Arg1 & arg1; const Arg2 & arg2; // ... const ArgN & argn; const int coef1; // I want to use const because const int coef2; // no modification is needed. int get_coef1() const { // calc coef1 using arg1, arg2, ..., argn; // undefined behavior? } int get_coef2() const { // calc coef2 using arg1, arg2, ..., argn and coef1; // undefined behavior? } }; struct Calc is not completely defined when I call get_coef1 and get_coef2 Is this code valid? Can I get UB?

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  • Why aren't operator conversions implicitly called for templated functions? (C++)

    - by John Gordon
    I have the following code: template <class T> struct pointer { operator pointer<const T>() const; }; void f(pointer<const float>); template <typename U> void tf(pointer<const float>); void g() { pointer<float> ptr; f(ptr); tf(ptr); } When I compile the code with gcc 4.3.3 I get a message (aaa.cc:17: error: no matching function for call to ‘tf(pointer<float>&)’) indicating that the compiler called 'operator pointer<const T>' for the non-templated function f(), but didn't for the templated function tf(). Why and is there any workaround short of overloading tf() with a const and non-const version? Thanks in advance for any help.

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  • How do I make the "back button" work with jQuery hide/show functions?

    - by Walker
    I'm looking for a way to append text to the url with jQuery so that the back button is not broken when a user loads new content with jQuery. For example, I have a three step form - the first step is (www.xyz.com/form-1). When the user clicks next step, jQuery slides in the next page. I would like that page to be (www.xyz.com/form-2). I know websites like hypem.com do this, I'm just looking for an elegant way to handle it.

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  • Are there any .net classes/functions that are optimized for multiple cores?

    - by diamandiev
    I know that the developer is supposed to do this himself. But seeing how we are getting cpu's with more and more cores and there are still many developers who do not use multithreading, if we have this functionality built in, it could increase performance dramatically in some scenarios. One particular example where this could be quite useful is in image processing. I doubt that the built in GDI+ classes are multithreaded.

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  • Why are closures broken within exec?

    - by Devin Jeanpierre
    In Python 2.6, >>> exec "print (lambda: a)()" in dict(a=2), {} 2 >>> exec "print (lambda: a)()" in globals(), {'a': 2} Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<string>", line 1, in <module> File "<string>", line 1, in <lambda> NameError: global name 'a' is not defined >>> exec "print (lambda: a).__closure__" in globals(), {'a': 2} None I expected it to print 2 twice, and then print a tuple with a single cell. It is the same situation in 3.1. What's going on?

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  • How to access 'private functions' in a singleton from another object inside it.

    - by Cedric Dugas
    I am currently trying to create a test suite for my javascript apps. My problem is that, it seems I cannot get access to init() from my utils object, as you can see below: I have my app that follow a singleton pattern: var appModal = function () { var utils = Object.create(moduleUtils); function init(caller, options ) { } }(); My test suite is in moduleUtils, this is a object literal converted to a prototype moduleUtils.debug = { addSlideTest : function(){ /* this function cannot fire init() from appModal */ }}

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  • Mutable global variables don't get hide in python functions, right?

    - by aXqd
    Please see the following code: def good(): foo[0] = 9 # why this foo isn't local variable who hides the global one def bad(): foo = [9, 2, 3] # foo is local, who hides the global one for func in [good, bad]: foo = [1,2,3] print('Before "{}": {}'.format(func.__name__, foo)) func() print('After "{}": {}'.format(func.__name__, foo)) The result is as below: # python3 foo.py Before "good": [1, 2, 3] After "good": [9, 2, 3] Before "bad" : [1, 2, 3] After "bad" : [1, 2, 3]

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  • Why do all procedures have to be defined before the compiler sees them?

    - by incrediman
    For example, take a look at this code (from tspl4): (define proc1 (lambda (x y) (proc2 y x))) If I run this as my program in scheme... #!r6rs (import (rnrs)) (define proc1 (lambda (x y) (proc2 y x))) I get this error: expand: unbound identifier in module in: proc2 ...This code works fine though: #!r6rs (import (rnrs)) (define proc2 +) (define proc1 (lambda (x y) (proc2 y x))) (display (proc1 2 3)) ;output: 5

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  • filtering elements from list of lists in Python?

    - by user248237
    I want to filter elements from a list of lists, and iterate over the elements of each element using a lambda. For example, given the list: a = [[1,2,3],[4,5,6]] suppose that I want to keep only elements where the sum of the list is greater than N. I tried writing: filter(lambda x, y, z: x + y + z >= N, a) but I get the error: <lambda>() takes exactly 3 arguments (1 given) How can I iterate while assigning values of each element to x, y, and z? Something like zip, but for arbitrarily long lists. thanks, p.s. I know I can write this using: filter(lambda x: sum(x)..., a) but that's not the point, imagine that these were not numbers but arbitrary elements and I wanted to assign their values to variable names.

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  • are C functions declared in <c____> headers gauranteed to be in the global namespace as well as std?

    - by Evan Teran
    So this is something that I've always wondered but was never quite sure about. So it is strictly a matter of curiosity, not a real problem. As far as I understand, what you do something like #include <cstdlib> everything (except macros of course) are declared in the std:: namespace. Every implementation that I've ever seen does this by doing something like the following: #include <stdlib.h> namespace std { using ::abort; // etc.... } Which of course has the effect of things being in both the global namespace and std. Is this behavior guaranteed? Or is it possible that an implementation could put these things in std but not in the global namespace? The only way I can think of to do that would be to have your libstdc++ implement every c function itself placing them in std directly instead of just including the existing libc headers (because there is no mechanism to remove something from a namespace). Which is of course a lot of effort with little to no benefit. The essence of my question is, is the following program strictly conforming and guaranteed to work? #include <cstdio> int main() { ::printf("hello world\n"); }

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