pack¶
Header¶
#include <boost/hof/pack.hpp>
Description¶
The pack function returns a higher order function object that takes a
function that will be passed the initial elements. The function object is
a sequence that can be unpacked with unpack_adaptor as well. Also,
pack_join can be used to join multiple packs together.
Synopsis¶
// Decay everything before capturing
template<class... Ts>
constexpr auto pack(Ts&&... xs);
// Capture lvalues by reference and rvalue reference by reference
template<class... Ts>
constexpr auto pack_forward(Ts&&... xs);
// Capture lvalues by reference and rvalues by value.
template<class... Ts>
constexpr auto pack_basic(Ts&&... xs);
// Join multiple packs together
template<class... Ts>
constexpr auto pack_join(Ts&&... xs);
Semantics¶
assert(pack(xs...)(f) == f(xs...));
assert(unpack(f)(pack(xs...)) == f(xs...));
assert(pack_join(pack(xs...), pack(ys...)) == pack(xs..., ys...));
Example¶
#include <boost/hof.hpp>
#include <cassert>
using namespace boost::hof;
struct sum
{
template<class T, class U>
T operator()(T x, U y) const
{
return x+y;
}
};
int main() {
int r = pack(3, 2)(sum());
assert(r == 5);
}