Can anyone describe the following declaration?
template<> float func<float>(char *txt) { blah blah } What is the second <> for?
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2 Answers
The template<> means that this function is a template specialization. The second <float> means that this is the specialization for float.
For example:
#include <iostream> template <class T> void somefunc(T arg) { std::cout << "Normal template called\n"; } template<> void somefunc<float>(float arg) { std::cout << "Template specialization called\n"; } int main(int argc, char *argv[]) { somefunc(1); // prints out "Normal template called" somefunc(1.0f); // prints out "Template specialization called" return 0; } 
Comments
This is a specialized template function. It happens when you try to specialized a generic template function. Usually you will have another deceleration as
template<typename T> float func(char *txt) { T vars[1024]; blah blah } It happens sometime you want to do a specialized declaration for certain type T. In previous example, if T is bool type, you might want to change the behavior of vars array to save some space (because each bool entry might still take 32bits).
template<> float func<bool>(char *txt) { int vars[32]; blah blah } By defining a specialized version, you are allowed to manipulate the vars array in bit-wise manner.
