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What is an invariant?
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An invariant is more "conceptual" than a variable. In general, it's a property of the program state that is always true. A function or method that ensures that the invariant holds is said to maintain the invariant.
For instance, a binary search tree might have the invariant that for eve...
How should I ethically approach user password storage for later plaintext retrieval?
As I continue to build more and more websites and web applications I am often asked to store user's passwords in a way that they can be retrieved if/when the user has an issue (either to email a forgotten password link, walk them through over the phone, etc.) When I can I fight bitterly against thi...
Unable to find the wrapper “https” - did you forget to enable it when you configured PHP?
...'ll list out exactly everything I've done so far. I am running PHP 5.2.14 with Zend Debugging on the latest Eclipse version on my Windows XP computer. I have a 1 GB of RAM. I have XAMPP running with Apache, MySQL, and FileZilla installed.
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Xcode 4 hangs at “Attaching to (app name)”
...ode 4 and for some reason my app won't run in the simulator or iOS device. It was working perfectly in Xcode 3, but all of a sudden now when I press run the program stops at "Attaching to...". There doesn't seem to be any other info to help with this problem either.
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How to get an IFrame to be responsive in iOS Safari?
... problem is that when you have to use IFrames to insert content into a website, then in the modern web-world it is expected that the IFrame would be responsive as well. In theory it's simple, simply aider use <iframe width="100%"></iframe> or set the CSS width to iframe { width: 100%;...
What is the significance of #pragma marks? Why do we need #pragma marks?
...to methods. They have no impact on the program at all.
For example, using it with Xcode 4 will make those items appear directly in the Jump Bar.
There is a special pragma mark - which creates a line.
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Obtaining a powerset of a set in Java
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Yes, it is O(2^n) indeed, since you need to generate, well, 2^n possible combinations. Here's a working implementation, using generics and sets:
public static <T> Set<Set<T>> powerSet(Set<T> originalSet) {...
How to order citations by appearance using BibTeX?
By default (using the plain style) BibTeX orders citations alphabetically.
12 Answers
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Can anyone explain what JSONP is, in layman terms? [duplicate]
I know JSONP is JSON with padding.
4 Answers
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Quickly reading very large tables as dataframes
...s a dataframes in R. read.table() has a lot of convenient features, but it seems like there is a lot of logic in the implementation that would slow things down. In my case, I am assuming I know the types of the columns ahead of time, the table does not contain any column headers or row names, an...