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  • How do I use "this" in a member function?

    - by Peter Stewart
    I've written a member function of class Node to read a tree of Nodes in postfix order. It will be called by the Node instance which is the root node of the tree. So: N.postfix(); these appear to be illeagal: *this->left.postfix(); *this->right.postfix(); What is the proper way to do this? class Node { public: const char *cargo; int depth; Node *left; Node *right void Node::postfix() { if (this==__nullptr) { return; } else { *this->left.postfix(); *this->right.postfix(); out<<*this->cargo<<"\n"; return; } };

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  • Generics List Interface...newb question

    - by newToProgramming
    The List interface is the following: public interface List<E>{ public boolean add(Object e); public boolean remove(Object e); public boolean contains(Object e); ...etc Why aren't the add, remove and contains methods written like the following? public boolean add(E e) public boolean remove(E e) public boolean contains(E e)

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  • How do Arrays work in C#?

    - by Slateboard
    I know that they are used to store data, but I have a difficult time understanding exactly how to use them in a program. In addition, I found this site with a tetris clone tutorial (the actual tutorial is missing). It uses arrays, but I can't really make sense of how it works. Here's an example of the code - public int[, ,] TShape = new int[4, 4, 2] { {{1, 0}, {0, 1}, {1, 1}, {2, 1}}, {{1, 0}, {0, 1}, {1, 1}, {1, 2}}, {{0, 0}, {1, 0}, {2, 0}, {1, 1}}, {{0, 0}, {0, 1}, {1, 1}, {0, 2}}}; Could it be that I'm looking too hard into this, or perhaps there's something I'm not grasping about it?

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  • How do you keep application logic separate from UI when UI components have built-in functionality?

    - by Al C
    I know it's important to keep user interface code separated from domain code--the application is easier to understand, maintain, change, and (sometimes) isolate bugs. But here's my mental block ... Delphi comes with components with methods that do what I want, e.g., a RichText Memo component lets me work with rich text. Other components, like TMS's string grid not only do what I want, but I paid extra for the functionality. These features put the R in RAD. It seems illogical to write my own classes to do things somebody else has already done for me. It's reinventing the wheel [ever tried working directly with rich text? :-) ] But if I use the functionality built into components like these, then I will end up with lots of intermingled UI and domain code--I'll have a form with most of my code built into its event handlers. How do you deal with this issue? ... Or, if I want to continue using the code others have already written for me, how would you suggest I deal with the issue?

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  • Make: how make all hidden files in the current makefile?

    - by HH
    It traverses to bottom dirs for some unknown reason: Errorsome /bin/sh: .??*: not found make[23]: Entering directory `/m/user/files/dir' make clean Makefile all: make clean #The wildcard is the bug. I want to make all hidden files in the current makefile. #It should match .<some char><some char><any char arbitrary times> make $$(.??*) #I want to replace below-like-tihngs with a wildcard above # make .lambda # make .lambda_t clean: -rm .??* .lambda: #do something .lambda_t:

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  • How do I create a new AnyType[] array?

    - by cb
    Which is the best practice in this situation? I would like an un-initialized array of the same type and length as the original. public static <AnyType extends Comparable<? super AnyType>> void someFunction(AnyType[] someArray) { AnyType[] anotherArray = (AnyType[]) new Comparable[someArray.length]; ...or... AnyType[] anotherArray = (AnyType[]) new Object[someArray.length]; ...some other code... } Thanks, CB

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  • Python - from file to data structure?

    - by Seafoid
    Hi, I have large file comprising ~100,000 lines. Each line corresponds to a cluster and each entry within each line is a reference i.d. for another file (protein structure in this case), e.g. 1hgn 1dju 3nmj 8kfn 9opu 7gfb 4bui I need to read in the file as a list of lists where each line is a sublist, thus preserving the integrity of the cluster, e.g. nested_list = [['1hgn', '1dju', '3nmj', '8kfn'], ['9opu', '7gfb'], ['4bui']] My current code creates a nested list but the entries within each list are a single string and not comma separated. Therefore, I cannot splice the list with indices so easily. Any help greatly appreciated. Thanks, S :-)

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  • What's the scope of a Python variable declared in an if statement?

    - by froadie
    I'm new to Python, so this is probably a simple scoping question. The following code in a Python file (module) is confusing me slightly: if __name__ == '__main__': x = 1 print x In other languages I've worked in, this code would throw an exception, as the x variable is local to the if statement and should not exist outside of it. But this code executes, and prints 1. Can anyone explain this behavior? Are all variables declared in a module global/available to the entire module?

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  • In what order should the Python concepts be explained to absolute beginners?

    - by Tomaž Pisanski
    I am teaching Python to undergraduate math majors. I am interested in the optimal order in which students should be introduced to various Python concepts. In my view, at each stage the students should be able to solve a non-trivial programming problem using only the tools available at that time. Each new tool should enable a simpler solution to a familiar problem. A selection of numerous concepts available in Python is essential in order to keep students focused. They should also motivated and should appreciate each newly mastered tool without too much memorization. Here are some specific questions: For instance, my predecessor introduced lists before strings. I think the opposite is a better solution. Should function definitions be introduced at the very beginning or after mastering basic structured programming ideas, such as decisions (if) and loops (while)? Should sets be introduced before dictionaries? Is it better to introduce reading and writing files early in the course or should one use input and print for most of the course? Any suggestions with explanations are most welcome.

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  • Returning currently displayed index of an array Javascript...

    - by Jeff Kindred
    I have a simple array with x number of items. I am displaying them individually via a link click... I want to update a number that say 1 of 10. when the next one is displayed i want it to display 2 of 10 etc... I have looked all around and my brain is fried right now... I know its simple I just cant get it out. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title>Page Title</title> <link rel="stylesheet" href="style.css" type="text/css" media="screen" charset="utf-8"/> <script type="text/javascript"> var quotations = new Array() quotations[0]= "1" quotations[1]= "2" quotations[2]= "3" quotations[3]= "4" quotations[4]= "5" quotations[5]= "6" quotations[6]= "7" numQuotes = quotations.length; curQuote = 1; function move( xflip ) { curQuote = curQuote + xflip; if (curQuote > numQuotes) { curQuote = 1 ; } if (curQuote == 0) { curQuote = numQuotes ; } document.getElementById('quotation').innerHTML=quotations[curQuote - 1]; } var curPage = //this is where the current index should go </script> </head> <body> <div id="quotation"> <script type="text/javascript">document.write(quotations[0]);</script> </div> <div> <p><a href="javascript();" onclick="move(-1)">GO back</a> <script type="text/javascript">document.write(curPage + " of " + numQuotes)</script> <a href="javascript();" onclick="move(1)">GO FORTH</a></p> </div> </body> </html>

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  • Regex, replace path to resource, modify resource name

    - by jerome
    Hi all, I'd like to use a JS regex to take a string such as the following: 'http://www.somedomain.com/some_directory/some_other_directory/some_image.jpg' And turn it into this: 'http://www.some_other_domain.com/another_directory/yet_another_directory/size1_some_image.jpg' Any hints? Additionally, any pointers for books or other resources that give a gentle introduction to mastering regexes in JS and other languages?

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  • How can I "override" deepcopy in Python?

    - by Az
    Hi there, I'd like to override __deepcopy__ for a given SQLAlchemy-mapped class such that it ignores any SQLA attributes but deepcopies everything else that's part of the class. I'm not particularly familiar with overriding any of Python's built-in objects in particular but I've got some idea as to what I want. Let's just make a very simple class User that's mapped using SQLA. class User(object): def __init__(self, user_id, name): self.user_id = user_id self.name = name I've used dir() to see, before and after mapping, what SQLAlchemy-specific attributes there are and I've found _sa_class_manager and _sa_instance_state. Provided those are the only ones how would I ignore that when defining __deepcopy__? Also, are there any attributes the SQLA injects into the mapped object? (I asked this in a previous question (as an edit a few days after I selected an answer to the main question, though) but I think I missed the train there. Apologies for that.)

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  • jQuery click event not working when mouse moves from one div to another with button held down

    - by Acorn
    I've made a page that uses jQuery to allow you to place <div>s on the page based on your mouse coordinates when you click. The page And here's the javascript: $('document').ready(function() { $("#canvas").click(function(e){ var x = e.pageX - this.offsetLeft; var y = e.pageY - this.offsetTop; $(document.createElement('div')).css({'left':x + 'px', 'top':y + 'px'}).addClass('tile').appendTo('#canvas'); }); }); I've found that if you mousedown in the div#canvas and mouseup with your pointer over a placed <div> (or vice versa) then a new <div> doesn't get placed. Why is this?

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  • Deleting an element from an array in perl

    - by Flamewires
    Hey I'm wondering how i can get this code to work, basically i want to keep the lines of $filename as long as they contain the $user in the path. Sry, perl noob. open STDERR, ">/dev/null"; $filename=`find -H /home | grep $file`; @filenames = split(/\n/, $filename); for $i (@filenames) { if ($i =~ m/$user/) { #keep results } else { delete $i; # does not work. } } $filename = join ("\n", @filenames); close STDERR; I know you can delete like delete $array[index] but I don't have an index with this kind of loop that I know of.

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  • What are good resources for computer graphics basics?

    - by Hanno Fietz
    During Flex programming, I recently ran into several questions (about box models, ways to join lines and misaligning pixels [on doctype]) regarding computer graphics and layout, where I felt that I lacked some basic background on things like concepts like the box model approaches mapping real numbers to a pixel raster (like font anti-aliasing) conventions found across drawing engines, like do you count y coordinates from top or bottom, and why I feel that reading some basic Wikipedia articles, books or tutorials on these subjects might help in phrasing my questions more specifically and debugging my code more systematically. I have repeatedly found myself writing tiny test apps in Flex, just to find out how the APIs do very basic stuff. My assumption would be that if I knew the right vocabulary and some general concepts, I could solve these questions much faster.

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  • In c++ is there any Events/delegates/interfaces/notifications! anything?

    - by Bach
    Say i have these classes ViewA and ViewB In objective C using the delegate pattern I could do @protocol ViewBDelegate{ - (void) doSomething(); } then in ViewB interface: id<ViewBDelegate> delegate; then in ViewA implementation i set the delegate: viewB.delegate = self; and now I can call in doSomething from viewB onto any that unknown type delegate. [delegate doSomething]; "C++ How to Program" has been the worse read an can't find simple examples that demonstrates basic design patterns. What i'm looking for in C++ is: events ActionScript and java either delegates or notifications in Objective C anything that allows class A, Class B and Class C to know that ClassX didSomething()!!! thanks

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  • How do I splice a python string programmatically?

    - by Robin Welch
    Very simple question, hopefully. So, in Python you can split up strings using indices as follows: >>> a="abcdefg" >>> print a[2:4] cd but how do you do this if the indices are based on variables? E.g. >>> j=2 >>> h=4 >>> print a[j,h] Traceback (most recent call last): File "<stdin>", line 1, in ? TypeError: string indices must be integers

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