Programming Forums > Application Development > C++

Jessehk · Aug 20th, 2007, 6:19 PM

http://www.sgi.com/tech/stl/table_of_contents.html

I don't know why I never realized it before, but the STL is really, really neat. The STL idea of concepts combined with boost::concept_traits allows you to check that template parameters pass certain requirements.

Example:

(Toggle Plain Text)

#include <iostream>
#include <vector>

#include <boost/concept_check.hpp>


template <typename InputIterator>
void display( InputIterator begin, InputIterator end ) {
    using namespace boost;
    
    function_requires<InputIteratorConcept<InputIterator> >();
    
    for (; begin != end; begin++ )
        std::cout << *begin;
    
    std::cout << std::endl;
}

int main() {
    std::vector<int> numbs;
    
    for ( int x = 0; x < 10; x++ )
        numbs.push_back( x );
    
    display( numbs.begin(), numbs.end() );
}

If I've done that right, it will only compile if the type of iterator passed to the display() function complies by the Input Iterator concept defined by the STL.

Here's another example:

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template <typename Integer>
bool isEven( Integer n ) {
    using namespace boost;
    
    function_requires<IntegerConcept<Integer> >();
    
    return !(n & 1);
}

int main() {
    std::cout << isEven( 314 ) << std::endl; // Is fine --> concept check passes
    std::cout << isEven( 4.2 ) << std::endl; // BAD --> compile error
}

C++ continues to astound me with what it's capable of. :eek:

Cache · Aug 21st, 2007, 4:44 AM

Quote:

Originally Posted by Jessehk

C++ continues to astound me with what it's capable of. :eek:

Then hold your pants on:
http://www.open-std.org/jtc1/sc22/wg...2005/n1758.pdf

Aug 20th, 2007, 6:19 PM	#1
Jessehk The Oblivious One Join Date: May 2005 Location: Ontario, Canada Posts: 644 Rep Power: 4	The STL is really neat http://www.sgi.com/tech/stl/table_of_contents.html I don't know why I never realized it before, but the STL is really, really neat. The STL idea of concepts combined with boost::concept_traits allows you to check that template parameters pass certain requirements. Example: (Toggle Plain Text) #include <iostream> #include <vector> #include <boost/concept_check.hpp> template <typename InputIterator> void display( InputIterator begin, InputIterator end ) { using namespace boost; function_requires<InputIteratorConcept<InputIterator> >(); for (; begin != end; begin++ ) std::cout << begin; std::cout << std::endl; } int main() { std::vector<int> numbs; for ( int x = 0; x < 10; x++ ) numbs.push_back( x ); display( numbs.begin(), numbs.end() ); } #include <iostream> #include <vector> #include <boost/concept_check.hpp> template <typename InputIterator> void display( InputIterator begin, InputIterator end ) { using namespace boost; function_requires<InputIteratorConcept<InputIterator> >(); for (; begin != end; begin++ ) std::cout << begin; std::cout << std::endl; } int main() { std::vector<int> numbs; for ( int x = 0; x < 10; x++ ) numbs.push_back( x ); display( numbs.begin(), numbs.end() ); } If I've done that right, it will only compile if the type of iterator passed to the display() function complies by the Input Iterator concept defined by the STL. Here's another example: (Toggle Plain Text) template <typename Integer> bool isEven( Integer n ) { using namespace boost; function_requires<IntegerConcept<Integer> >(); return !(n & 1); } int main() { std::cout << isEven( 314 ) << std::endl; // Is fine --> concept check passes std::cout << isEven( 4.2 ) << std::endl; // BAD --> compile error } template <typename Integer> bool isEven( Integer n ) { using namespace boost; function_requires<IntegerConcept<Integer> >(); return !(n & 1); } int main() { std::cout << isEven( 314 ) << std::endl; // Is fine --> concept check passes std::cout << isEven( 4.2 ) << std::endl; // BAD --> compile error } C++ continues to astound me with what it's capable of. :eek: __________________ Dr. Zoidberg: [ecstatic] I'm going to a movie... with FRIENDS!

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Programming Forums > Application Development > C++

The STL is really neat