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What is in your Mathematica tool bag? [closed]
...ned this before, but the tool I find most useful is an application of Reap and Sow which mimics/extends the behavior of GatherBy:
SelectEquivalents[x_List,f_:Identity, g_:Identity, h_:(#2&)]:=
Reap[Sow[g[#],{f[#]}]&/@x, _, h][[2]];
This allows me to group lists by any criteria and tran...
What are file descriptors, explained in simple terms?
... open a file, the operating system creates an entry to represent that file and store the information about that opened file. So if there are 100 files opened in your OS then there will be 100 entries in OS (somewhere in kernel). These entries are represented by integers like (...100, 101, 102....). ...
Synchronizing a local Git repository with a remote one
...er in these repositories, we override the local ones with the remote ones, and if there are files in local repositories that do not exist in the remote, the local files get removed.
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What is the difference between HTTP status code 200 (cache) vs status code 304?
... cache them (e.g. future-dated Expires or Cache-Control: max-age headers), and that at the time you triggered the new request, those cached objects were still stored in local cache and had not yet expired.
304s, on the other hand, are the response of the server after the browser has checked if a fi...
Can code that is valid in both C and C++ produce different behavior when compiled in each language?
C and C++ have many differences, and not all valid C code is valid C++ code.
(By "valid" I mean standard code with defined behavior, i.e. not implementation-specific/undefined/etc.)
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Can every recursion be converted into iteration?
...u always turn a recursive function into an iterative one? Yes, absolutely, and the Church-Turing thesis proves it if memory serves. In lay terms, it states that what is computable by recursive functions is computable by an iterative model (such as the Turing machine) and vice versa. The thesis does ...
Do htmlspecialchars and mysql_real_escape_string keep my PHP code safe from injection?
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When it comes to database queries, always try and use prepared parameterised queries. The mysqli and PDO libraries support this. This is infinitely safer than using escaping functions such as mysql_real_escape_string.
Yes, mysql_real_escape_string is effectively just a ...
What is the difference between “screen” and “only screen” in media queries?
What is the difference between screen and only screen in media queries?
5 Answers
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Can a foreign key be NULL and/or duplicate?
...als. Suppose further that each proposal only has one sales person assigned and one client. So your proposal table would have two foreign keys, one with the client ID and one with the sales rep ID. However, at the time the record is created, a sales rep is not always assigned (because no one is fre...
How can I delete a file from a Git repository?
...y. After that, I committed it, added a couple of directories called dir1 and dir2 , and committed them to the Git repository.
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