C++ for Scientists - Technische Universität Dresden

4.11. EXERCISES 129
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function gcd(a, b):
if b = 0 return a
else return gcd(b, a mod b)
Then write an integral metafunction that executes the same algorithm but at compile time.
Your metafunction should be of the following form:
template
struct gcd meta {
static int const value = ... ;
} ;
i.e. gcd meta::value is the GCD of a and b. Verify whether the results correspond with your
C ++ function gcd().
4.11.6 Overloading of functions
Overloading of functions is possible for different types, e.g.
void foo( int i ) { ... }
void foo( double d ) { ... }
This is an exercise on another form of overloading: based on a boolean meta expression. We
will use the Boost functions enable if and disable if for this exercise.
#include
#include
template
typename boost::enable if< boost::is integral, T >::type foo( T const& v ) {
return v ;
}
template
typename boost::disable if< boost::is integral, T >::type foo( T const& v ) {
return std::floor( v ) ;
}
If we call e.g. foo(5);, the compiler uses the special version for integers:
template
T foo( T const& v ) {
return v ;
}
If we call e.g. foo(5.0);, the compiler uses the special version for types that are not integral:
template
T foo( T const& v ) {
return std::floor( v ) ;
}