Type Traits

Provides various type traits and their shortcuts. More...

Collaboration diagram for Type Traits:

Classes
struct	bio::meta::is_type_specialisation_of< source_t, target_template >
	Determines whether a source_type is a specialisation of another template. More...
struct	bio::meta::is_value_specialisation_of< source_t, target_template >
	Provides concept bio::meta::template_specialisation_of<mytype, [...]> for checking the type specialisation of some type with a given template, for example a specialized type_list<float> with the type_list template. More...
struct	bio::meta::transfer_template_args_onto< source_template< source_arg_types... >, target_template >
	Extracts a type template's type arguments and specialises another template with them. More...
struct	bio::meta::transfer_template_vargs_onto< source_template< source_varg_types... >, target_template >
	Extracts a type template's non-type arguments and specialises another template with them. More...
struct	bio::meta::valid_template_spec_or< fallback_t, templ_t, spec_t >
	Exposes templ_t<spec_t...> if that is valid, otherwise fallback_t. More...

Concepts
concept	bio::meta::transformation_trait
	Concept for a transformation trait.
concept	bio::meta::unary_type_trait
	Concept for a unary traits type.

Macros
#define	BIOCPP_IS_CONSTEXPR(...)   std::integral_constant<bool, __builtin_constant_p((__VA_ARGS__, 0))>::value
	Returns true if the expression passed to this macro can be evaluated at compile time, false otherwise.
#define	BIOCPP_IS_SAME(...)   std::is_same_v<__VA_ARGS__>
	A macro that behaves like std::is_same_v, except that it doesn't need to instantiate the template on GCC and Clang.

Typedefs
template<typename t >
using	default_initialisable_wrap_t = std::conditional_t< std::is_nothrow_default_constructible_v< std::remove_cvref_t< t > > &&constexpr_default_initializable< std::remove_cvref_t< t > >, std::remove_cvref_t< t >, std::type_identity< std::remove_cvref_t< t > > >
	Return t as t if it is noexcept- and constexpr-default-constructible; else wrap it in std::type_identity.
using	bio::meta::ignore_t = std::remove_cvref_t< decltype(std::ignore)>
	Return the type of std::ignore with const, volatile and references removed (type trait).
template<typename t >
using	bio::meta::strip_type_identity_t = std::conditional_t< is_type_specialisation_of_v< t, std::type_identity >, transformation_trait_or_t< t, void >, t >
	A transformation trait shortcut that returns the type inside a std::type_identity or the type itself.
template<typename source_type , template< typename... > typename target_template>
using	bio::meta::transfer_template_args_onto_t = typename transfer_template_args_onto< source_type, target_template >::type
	Shortcut for bio::meta::transfer_template_args_onto (transformation_trait shortcut).
template<typename source_type , template< auto... > typename target_template>
using	bio::meta::transfer_template_vargs_onto_t = typename transfer_template_vargs_onto< source_type, target_template >::type
	Shortcut for bio::meta::transfer_template_vargs_onto (transformation_trait shortcut).
template<typename type_t , typename default_t >
using	bio::meta::transformation_trait_or = std::conditional_t< transformation_trait< type_t >, type_t, std::type_identity< default_t > >
	This gives a fallback type if type_t::type is not defined.
template<typename type_t , typename default_t >
using	bio::meta::transformation_trait_or_t = typename transformation_trait_or< type_t, default_t >::type
	Helper type of bio::meta::transformation_trait_or (transformation_trait shortcut).
template<typename fallback_t , template< typename... > typename templ_t, typename... spec_t>
using	bio::meta::valid_template_spec_or_t = typename valid_template_spec_or< fallback_t, templ_t, spec_t... >::type
	Helper for bio::meta::valid_template_spec_or (transformation_trait shortcut).

Variables
template<typename... t>
constexpr bool	bio::meta::always_false = false
	A trait that is always false. Can be used for static_assert(false). DO NOT SPECIALISE!
template<typename t >
constexpr bool	bio::meta::decays_to_ignore_v = std::is_same_v<std::remove_cvref_t<t>, ignore_t>
	Return whether the input type with const, volatile and references removed is std::ignore's type. (type trait).

Detailed Description

Provides various type traits and their shortcuts.

Macro Definition Documentation

BIOCPP_IS_CONSTEXPR

#define BIOCPP_IS_CONSTEXPR

(

...

)

std::integral_constant<bool, __builtin_constant_p((__VA_ARGS__, 0))>::value

Returns true if the expression passed to this macro can be evaluated at compile time, false otherwise.

Returns

true or false.

Typedef Documentation

default_initialisable_wrap_t

template<typename t >

using default_initialisable_wrap_t = std::conditional_t<std::is_nothrow_default_constructible_v<std::remove_cvref_t<t> > && constexpr_default_initializable<std::remove_cvref_t<t> >, std::remove_cvref_t<t>, std::type_identity<std::remove_cvref_t<t> >>

Return t as t if it is noexcept- and constexpr-default-constructible; else wrap it in std::type_identity.

Template Parameters

t	The type to operate on.

strip_type_identity_t

template<typename t >

using bio::meta::strip_type_identity_t = typedef std::conditional_t<is_type_specialisation_of_v<t, std::type_identity>, transformation_trait_or_t<t, void>, t>

A transformation trait shortcut that returns the type inside a std::type_identity or the type itself.

Template Parameters

t	The type to operate on.

transfer_template_args_onto_t

template<typename source_type , template< typename... > typename target_template>

using bio::meta::transfer_template_args_onto_t = typedef typename transfer_template_args_onto<source_type, target_template>::type

Shortcut for bio::meta::transfer_template_args_onto (transformation_trait shortcut).

See also

bio::meta::transfer_template_args_onto

transfer_template_vargs_onto_t

template<typename source_type , template< auto... > typename target_template>

using bio::meta::transfer_template_vargs_onto_t = typedef typename transfer_template_vargs_onto<source_type, target_template>::type

Shortcut for bio::meta::transfer_template_vargs_onto (transformation_trait shortcut).

See also

bio::meta::transfer_template_vargs_onto

transformation_trait_or

template<typename type_t , typename default_t >

using bio::meta::transformation_trait_or = typedef std::conditional_t<transformation_trait<type_t>, type_t, std::type_identity<default_t> >

This gives a fallback type if type_t::type is not defined.

Template Parameters

type_t	The type to use if type_t::type is defined.
default_t	The type to use otherwise.

See also

bio::meta::transformation_trait_or_t

Gives type_t back if T::type is a member type, otherwise struct{using type = default_t}.

#include <bio/meta/type_traits/transformation_trait_or.hpp>
 
template <typename T>
struct A;
 
template <>
struct A<int>
{
    using type = int;
};
 
// A<unsigned>::type is not defined, thus falling back to `void`
static_assert(std::is_same_v<void, bio::meta::transformation_trait_or_t<A<unsigned>, void>>);
 
// A<int>::type is defined, use A<int>::type
static_assert(std::is_same_v<int, bio::meta::transformation_trait_or_t<A<int>, void>>);

Attention

This might get removed if one of our used libraries offers the same functionality.

Helper types

bio::meta::transformation_trait_or_t as a shorthand for typename bio::meta::transformation_trait_or::type

transformation_trait_or_t

template<typename type_t , typename default_t >

using bio::meta::transformation_trait_or_t = typedef typename transformation_trait_or<type_t, default_t>::type

Helper type of bio::meta::transformation_trait_or (transformation_trait shortcut).

See also

bio::meta::transformation_trait_or

valid_template_spec_or_t

template<typename fallback_t , template< typename... > typename templ_t, typename... spec_t>

using bio::meta::valid_template_spec_or_t = typedef typename valid_template_spec_or<fallback_t, templ_t, spec_t...>::type

Helper for bio::meta::valid_template_spec_or (transformation_trait shortcut).

See also

bio::meta::valid_template_spec_or

Template Parameters

fallback_t	The fallback type.
templ_t	The type template that should be specialised.
spec_t	The specialisation for the type template.

Variable Documentation

decays_to_ignore_v

template<typename t >

constexpr bool bio::meta::decays_to_ignore_v = std::is_same_v<std::remove_cvref_t<t>, ignore_t>

inlineconstexpr

Return whether the input type with const, volatile and references removed is std::ignore's type. (type trait).

Template Parameters

t	The type to operate on.