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Is PHP's count() function O(1) or O(n) for arrays?
...unt the all the elements of a PHP array, or is this value cached somewhere and just gets retrieved?
3 Answers
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What's the purpose of SQL keyword “AS”?
...ll keyword. As example: JDBC 4.0. Depending of using aliases w/ 'AS cause' and w/o you will receive different behavior - see this answer stackoverflow.com/a/4271250/814304. I would like to recommend ALWAYS use the full form of semantic to avoid such issues.
– iMysak
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Build .so file from .c file using gcc command line
...llo.c -o hello.o
This will generate an object file (.o), now you take it and create the .so file:
gcc hello.o -shared -o libhello.so
EDIT: Suggestions from the comments:
You can use
gcc -shared -o libhello.so -fPIC hello.c
to do it in one step. – Jonathan Leffler
I also suggest to add -W...
What's the difference between deadlock and livelock?
... explain with examples (of code) what is the difference between deadlock and livelock ?
7 Answers
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Shell脚本编程30分钟入门 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...文本编辑器和一个能解释执行的脚本解释器就可以了。
OS
当前主流的操作系统都支持shell编程，本文档所述的shell编程是指Linux下的shell，讲的基本都是POSIX标准下的功能，所以，也适用于Unix及BSD（如Mac OS）。
Linux
Linux默认安...
Get index of array element faster than O(n)
Given I have a HUGE array, and a value from it. I want to get index of the value in array. Is there any other way, rather then call Array#index to get it? The problem comes from the need of keeping really huge array and calling Array#index enormous amount of times.
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How do I fix the Visual Studio compile error, “mismatch between processor architecture”?
...project configuration in Visual Studio 2010, but I've done some research and still can't quite figure this issue out. I have a Visual Studio solution with a C++ DLL referencing the C# DLL. The C# DLL references a few other DLLs, some within my project and some external. When I try to compile the C...
How to compile a static library in Linux?
...e into a file named out.a. Is it sufficient to simply compile with the command gcc -o out.a out.c ? I'm not quite familiar with gcc , hope anyone can give me a hand.
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What is `mt=8` in iTunes links for the App Store?
...menter above, in case you haven't figured out, ls=1 means the URL will try and open iTunes and follow the link. If ls=1 is not included it will simply load the web page for that particular media asset.
– Rog
Feb 3 '12 at 0:14
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Can't find the 'libpq-fe.h header when trying to install pg gem
...nx), 11.10 (Oneiric Ocelot), 12.04 (Precise Pangolin), 14.04 (Trusty Tahr) and 18.04 (Bionic Beaver)):
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/usr/include/postgresql/libpq-fe.h
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So try installing libpq-dev or its equivalent for your OS:
For Ubuntu/Debian systems: sudo apt-get install libpq-dev
On Red Hat Linux (RHEL) systems:...