variadic-helper.hpp File Reference

Metaprogramming with type sequences based on variadic template parameters. More...

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Description

Metaprogramming with type sequences based on variadic template parameters.

The type rebinding- and helper templates in this header allow to perform simple sequence manipulations on sequences of template parameters extracted from variadic parameter packs. The goal is to (pre)process flexible argument lists at compile time, driven by template instantiation, allowing to specialise and react specifically on some concrete pattern of argument types.

Remarks

in Lumiera, over time three different approaches were developed for handling sequences of types in metaprogramming; some of these techniques are better suited for specific kinds of tasks than others

• templates with variadic arguments (e.g. std::tuple) can be manipulated directly
• a type-sequence Types<T...> can be primed / rebound from other variadic templates
• Loki-style type-lists are created from type-sequences and enable elaborate manipulations

See also

feed-manifold.hpp advanced usage example in the Render Engine

TupleHelper_test

typelist.hpp

function.hpp

generator.hpp

Definition in file variadic-helper.hpp.

#include "lib/meta/typelist.hpp"
#include "lib/meta/typelist-util.hpp"
#include "lib/meta/typeseq-util.hpp"
#include "lib/meta/variadic-rebind.hpp"
#include "lib/meta/util.hpp"

Namespaces
namespace	lib
	Implementation namespace for support and library code.
namespace	lib::meta
namespace	lib::meta::anonymous_namespace{variadic-helper.hpp}

Classes
struct	IndexSeq< idx >
	Hold a sequence of index numbers as template parameters. More...
struct	BuildIndexSeq< n >
	build regular sequences of index number e.g. More...
struct	BuildIndexSeq< 0 >
struct	BuildIdxIter< TYPES >
	build a sequence of index numbers based on a type sequence More...
struct	BuildIdxIter< Types< TYPES... > >
	build an index number sequence from a type sequence More...
struct	ElmTypes< X, typename >
	Variadic type sequence builder. More...
struct	ElmTypes< Types< TYPES... > >
	Partial specialisation to handle type sequences. More...
class	WithIdxSeq< N >
	helper to invoke a functor, passing instances of std::integral_constant More...
struct	SelectVararg< i >
struct	SelectVararg< 0 >
struct	SelectOrInit< bool, typename, idx >
struct	SelectOrInit< false, DEFAULT, idx >

Functions
template<class TTX , class FUN >
void	forEachIDX (FUN &&fun)
	Invoke a function (or λ) with index numbers derived from some variadic count.
template<class TTX , class FUN >
bool	andAllIDX (FUN &&fun)
template<class TTX , class FUN >
bool	orAnyIDX (FUN &&fun)
template<size_t idx, typename... ARGS>
constexpr auto	pickArg (ARGS &&... args)
	Helper to single out one argument from a variadic argument pack.
template<size_t idx, typename DEFAULT , typename... ARGS>
constexpr auto	pickInit (ARGS &&... args)
	Helper to pick one initialisation argument from a variadic argument pack, falling back to a default constructed element of type DEFAULT in case of insufficient number of variadic arguments.

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Class Documentation

lib::meta::IndexSeq

struct lib::meta::IndexSeq

Class Members
typedef IndexSeq< idx..., i >	AppendElm
typedef IndexSeq< i, idx... >	PrependElm

Collaboration diagram for IndexSeq< idx >:

lib::meta::BuildIndexSeq

struct lib::meta::BuildIndexSeq

Class Members
typedef template AppendElm< n-1 >	Ascending
typedef template PrependElm< n-1 >	Descending
typedef template template AppendElm< n-1+d >	OffsetBy
typedef template template AppendElm< x >	FilledWith
typedef Ascending	First
typedef BuildIndexSeq<(n >c)? n-c :0 >::template OffsetBy< c >	After

Collaboration diagram for BuildIndexSeq< n >:

lib::meta::BuildIndexSeq< 0 >

struct lib::meta::BuildIndexSeq< 0 >

Class Members
typedef IndexSeq<>	EmptySeq
typedef EmptySeq	Ascending
typedef EmptySeq	Descending
typedef EmptySeq	OffsetBy
typedef EmptySeq	FilledWith
typedef EmptySeq	First
typedef EmptySeq	After

Collaboration diagram for BuildIndexSeq< 0 >: