basic_functionality.md

Basic Functionality

TypePack offers an API for manipulating it and generating a new TypePack with modifications.

Once all modifications are done you can unpack TypePack to use it in a Builder.

ADD

Add a new type to an existing TypePack:

// Existing TypePack with only one type.
using base = meta::TypePack<int>;

// add_t<type> allows create a new TypePack whith new type added.
using final = base::add_t<float>;

POP

Remove types from the back of an existing TypePack:

// Existing TypePack with 3 types.
using base = meta::TypePack<int, float, long>;

// pop_t<N> remove N elements from the back of base.
using final = base::pop_t<2>;

GET

Get type from TypePack by index:

// Existing TypePack with 3 types.
using base = meta::TypePack<int, std::string, long>;

// get<1> returns std::string type.
typename base::get<1> name = "my name";

GET_VAL

Get value from TypePack by index:

// Existing TypePack with 3 Constant types.
using base = meta::TypePack<meta::Constant<size_t, 0>,
                    meta::Constant<size_t, 1>,
                    meta::Constant<size_t, 2>>;

// get_val<1> returns 1.
auto name = base::get_val<1>;