Bind.md

<CppML/Functional/Bind.hpp>

Table of Contents

• Par
• Bind

Par

template <int I, typename T>
struct Par;

Par<I, T>

Par<I, T> is a parameter holder for ml::Bind, where I specifies the position of T, when the bound metafunction is invoked.

NOTE

Aliases of the form

template <typename T>
using _p0 = Par<0, T>;

are defined in the range [0, 20].

Bind

template <typename F, int ...Is, typename ...Args>
struct Bind<F, ml::Par<Is, Args>...> {
  template <typename ...Ts>
  using f = /* .... */;
};

Bind<F, Par<Is, Args>...>

Bind<F, Par<Is, Args>...> is a metafunction, that is a partial evaluation of F , with Args... bound to positions Is.... When invoked on Ts..., it is as if F was invoked on Us..., which was generated by inserting each element of Args... in Is... position in Ts....

f:: Ts... -> F(Us...)

NOTE

ml::Par<Is, Args>... must appear in ascending sorted order (by int ...Is).

Example

To make the example explicit, we bind ml::Int in their corresponding positions for ml::ToList, and invoke it on the rest.

using Bound = ml::Bind<
                ml::ToList,
                ml::_p1<ml::Int<1>>,
                ml::_p3<ml::Int<3>>>;

using T = ml::f<
              Bound,
              ml::Int<0>, ml::Int<2>, ml::Int<4>>; 

static_assert(
        std::is_same_v<
                T0,
                ml::ListT<
                  ml::Int<0>, ml::Int<1>, ml::Int<2>, ml::Int<3>, ml::Int<4>>>);