Working on some code for my research tonight, I wasted a lot of time looking for some information on a particlar STL function. Since I couldn’t find the answers elsewhere, I am posting a quick explanation/solution here, to hopefully save someone else the trouble.
I am writing a C++ application, and use the STL in various places. I have been consulting the SGI Standard Template Library Programmer’s Guide. It is quite poorly named; it is really a reference, with not much guidance at all. And unfortunately I have yet to find a decent book on the STL (I have one but it sucks).
(Note that the below applies to the
g++ compiler version 3.3; I don’t know about other compilers or libraries.)
Anyway, I found just the function I was after:
random_sample_n. So I added the include for algorithm, and couldn’t get the sucker to compile. It turns out that since it is an extension to the STL, it is located in the
ext/algorithm header, and under the namespace
__gnu_cxx:: instead of
std::. This stuff I found the hard way, slugging through header files.
Another thing: I didn’t find any decent examples (the one in the SGI docs is trivial) so here is some real code:
Nowdays, there is the most excellent http://www.cppreference.com/ which has a comprehensive reference for all the STL and standard C++ library classes, methods and functions.
And the new C++11 standard features e whole module for generating random numbers.