variadic-rebind.hpp File Reference

Metaprogramming support to rebuild and rebind variadic templates. More...

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Description

Metaprogramming support to rebuild and rebind variadic templates.

The sequence of variadic arguments itself is often difficult to manipulate, because a parameter pack is not a type proper in C++, but rather some meta mapping expanded immediately by the compiler. For more elaborate processing, this sequence must thus be re-mapped into a format that allows to pass partial results from recursive evaluations (since all of this »processing« is actually a form of functional programming).

For many simple cases though it is sufficient just to re-bind a template to another template's variadic sequence, possibly with some basic manipulation. Such a meta-processing can be coded very succinctly, by passing the target template to receive the altered sequence as a template-template parameter.

Warning

this kind of recursive remoulding typically imposes an O(n) effort during compilation, sometimes even O(n²) (notably reversing a sequence). Thus be sure to apply to short type sequences only endcode

Usage example

template<typename...CASES>
struct MyModel
  {
    using SubSeq = _Vari<MyModel, CASES...>::Prefix;
 
    // adapt a predecessor sequence
    MyModel (SubSeq&& subModel);
 
 
    using Tuple = RebindVariadic<std::tuple, CASES...>::Type;
  }

See also

param-weaving-pattern.hpp "usage example"

util::parse::AltModel "usage example"

typelist.hpp

function.hpp

Definition in file variadic-rebind.hpp.

Namespaces
namespace	lib
	Implementation namespace for support and library code.
namespace	lib::meta

Classes
struct	RebindVariadic< X, ARGS >
	Metaprogramming helper to transfer variadic arguments. More...
struct	RebindVariadic< X, U< ARGS... > >
struct	_Vari< L, X, L< XS... > >
struct	_Vari< L, X1, X2 >
struct	_Vari< L, X >
struct	_Vari< L, X, XS... >

---

Class Documentation

lib::meta::RebindVariadic

struct lib::meta::RebindVariadic

Class Members
typedef X< ARGS... >	Type

Collaboration diagram for RebindVariadic< X, ARGS >:

lib::meta::RebindVariadic< X, U< ARGS... > >

struct lib::meta::RebindVariadic< X, U< ARGS... > >

Class Members
typedef X< ARGS... >	Type

Collaboration diagram for RebindVariadic< X, U< ARGS... > >:

lib::meta::_Vari< L, X, L< XS... > >

struct lib::meta::_Vari< L, X, L< XS... > >

Class Members
typedef L< X, XS... >	Prepend
typedef L< XS..., X >	Append

Collaboration diagram for _Vari< L, X, L< XS... > >:

lib::meta::_Vari< L, X1, X2 >

struct lib::meta::_Vari< L, X1, X2 >

Class Members
typedef X1	Penult
typedef X2	Ultima
typedef L< X1 >	Prefix
typedef L< X2 >	Remain
typedef L< X2, X1 >	Revers

Collaboration diagram for _Vari< L, X1, X2 >:

lib::meta::_Vari< L, X >

struct lib::meta::_Vari< L, X >

Class Members
typedef X	Ultima
typedef Nil	Penult	marker for undefined
typedef L< X >	Remain
typedef L< X >	Revers
typedef L<>	Prefix

Collaboration diagram for _Vari< L, X >:

lib::meta::_Vari< L, X, XS... >

struct lib::meta::_Vari< L, X, XS... >

Class Members
typedef Penult	Penult
typedef Ultima	Ultima
typedef Prefix	_Tail_Pre_
typedef Revers	_Tail_Rev_
typedef L< XS... >	Remain
typedef Prepend	Prefix
typedef Prepend	Revers

Collaboration diagram for _Vari< L, X, XS... >: