Re: Is there a way to span a suite of explicit instantiations automatically?
Avner wrote:
Hi,
I am creating a template library for a template class with two template
arguments.
Is there a way to span a suite of explicit instantiation, instead of
having to specify all the combinations of the template arguments
specifically?
Say I have a class
template <class T1, class T2>
class Foo
{
T1 t1;
T2 t2;
}
with T1, T2 having the following possibilities:
T1 - unsigned char, short, unsigned short, long
T2 - unsigned char, short, float, double
I was thinking of some way like a function that scans all the
combinations and constructs the class for each of the combinations.
Maybe having the function as static will force the generation of the
code, which will force the generation of the class code for each
combination of the template arguments.
Something like:
template <class S1, class D>
static void foo()
{
loop on all T1 possibilities
{
loop on all T2 possibilities
{
Foo<T1, T2> *p = new Foo<T1, T2>;
}
}
}
You can do that with boost::mpl:
$ cat exp.cpp
#include <stdio.h>
#include <boost/mpl/vector.hpp>
#include <boost/mpl/for_each.hpp>
namespace m = boost::mpl;
template<class T1, class T2> struct some {};
typedef m::vector<unsigned char, short, unsigned short, long> ones;
typedef m::vector<unsigned char, short, float, double> twos;
template<class T>
void foo(m::identity<T>)
{
printf("%s\n", __PRETTY_FUNCTION__);
}
template<class T1>
struct step_two
{
template<class T2>
void operator()(m::identity<T2>)
{
foo(m::identity<some<T1, T2> >());
}
};
struct step_one
{
template<class T1>
void operator()(m::identity<T1>)
{
m::for_each<twos, m::make_identity<m::_> >(step_two<T1>());
}
};
int main()
{
m::for_each<ones, m::make_identity<m::_> >(step_one());
}
$ make
g++ -I../ -fmessage-length=0 -Wall -Wextra -ggdb -c exp.cpp -o exp.o
g++ -o exp exp.o
$ ./exp
void foo(boost::mpl::identity<T>) [with T = some<unsigned char,
unsigned char>]
void foo(boost::mpl::identity<T>) [with T = some<unsigned char, short
int>]
void foo(boost::mpl::identity<T>) [with T = some<unsigned char, float>]
void foo(boost::mpl::identity<T>) [with T = some<unsigned char,
double>]
void foo(boost::mpl::identity<T>) [with T = some<short int, unsigned
char>]
void foo(boost::mpl::identity<T>) [with T = some<short int, short int>]
void foo(boost::mpl::identity<T>) [with T = some<short int, float>]
void foo(boost::mpl::identity<T>) [with T = some<short int, double>]
void foo(boost::mpl::identity<T>) [with T = some<short unsigned int,
unsigned char>]
void foo(boost::mpl::identity<T>) [with T = some<short unsigned int,
short int>]
void foo(boost::mpl::identity<T>) [with T = some<short unsigned int,
float>]
void foo(boost::mpl::identity<T>) [with T = some<short unsigned int,
double>]
void foo(boost::mpl::identity<T>) [with T = some<long int, unsigned
char>]
void foo(boost::mpl::identity<T>) [with T = some<long int, short int>]
void foo(boost::mpl::identity<T>) [with T = some<long int, float>]
void foo(boost::mpl::identity<T>) [with T = some<long int, double>]
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