Type Traits

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

Collaboration diagram for Type Traits:

Classes
struct	seqan3::detail::deferred_type< t, dependent_ts >
	Return the type identity; further arguments are ignored, but can make this type dependent if they are. More...
struct	seqan3::function_traits< std::function< return_t(args_t...)> >
	A traits class to provide a uniform interface to the properties of a function type. More...
struct	seqan3::detail::instantiate< t >
	A transformation trait that instantiates seqan3::lazy types. Base template is the identity transformation. More...
struct	seqan3::detail::instantiate< lazy< template_t, spec_t... > >
	A transformation trait that instantiates seqan3::lazy types. More...
struct	seqan3::detail::instantiate_if< t, condition >
	A transformation trait that instantiates seqan3::lazy types given a boolean condition. Base template is std::false_type. More...
struct	seqan3::detail::instantiate_if< lazy< template_t, spec_t... >, true >
	A transformation trait that instantiates seqan3::lazy types given a boolean condition. If condition is true and parameter is lazy, the instantiated type. More...
struct	seqan3::detail::instantiate_if< t, true >
	A transformation trait that instantiates seqan3::lazy types given a boolean condition. If condition is true and parameter is not lazy, the type identity. More...
struct	seqan3::is_constexpr_default_constructible< t >
	Whether a type std::is_default_constructible in constexpr-context (unary_type_trait specialisation). More...
struct	seqan3::detail::lazy< template_t, spec_t >
	An empty type whose only purpose is to hold an uninstantiated template plus its arguments. More...
struct	seqan3::detail::lazy_conditional< decision, on_true_t, on_false_t >
	Behaves like std::conditional, but instantiates types wrapped in seqan3::lazy. More...
struct	seqan3::remove_rvalue_reference< t >
	Return the input type with && removed, but lvalue references preserved. More...
interface	transformation_trait
	Concept for a transformation trait. More...
interface	unary_type_trait
	Concept for a unary traits type. More...

Macros
#define	SEQAN3_IS_CONSTEXPR(...)   std::integral_constant<bool, __builtin_constant_p(((void)__VA_ARGS__, 0))>::value
	Returns true if the expression passed to this macro can be evaluated at compile time, false otherwise.
#define	SEQAN3_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 , typename... dependent_ts>
using	seqan3::detail::deferred_type_t = typename deferred_type< t, dependent_ts... >::type
	Return the type identity; further arguments are ignored, but can make this type dependent if they are (transformation_trait shortcut).
using	seqan3::detail::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 type_t , typename default_t >
using	seqan3::detail::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	seqan3::detail::transformation_trait_or_t = typename transformation_trait_or< type_t, default_t >::type
	Helper type of seqan3::detail::transformation_trait_or (transformation_trait shortcut).

Variables
template<typename t >
constexpr bool	seqan3::detail::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.

See also

Utility

Macro Definition Documentation

SEQAN3_IS_CONSTEXPR

#define SEQAN3_IS_CONSTEXPR

(

...

)

std::integral_constant<bool, __builtin_constant_p(((void)__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

deferred_type_t

template<typename t , typename... dependent_ts>

using seqan3::detail::deferred_type_t = typedef typename deferred_type<t, dependent_ts...>::type

Return the type identity; further arguments are ignored, but can make this type dependent if they are (transformation_trait shortcut).

Template Parameters

t	The type to operate on.
dependent_ts	Any provided types are ignored.

See also

seqan3::detail::deferred_type

transformation_trait_or

template<typename type_t , typename default_t >

using seqan3::detail::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

seqan3::detail::transformation_trait_or_t

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

// SPDX-FileCopyrightText: 2006-2024 Knut Reinert & Freie Universität Berlin
// SPDX-FileCopyrightText: 2016-2024 Knut Reinert & MPI für molekulare Genetik
// SPDX-License-Identifier: CC0-1.0
 
#include <seqan3/utility/type_traits/detail/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, seqan3::detail::transformation_trait_or_t<A<unsigned>, void>>);
 
// A<int>::type is defined, use A<int>::type
static_assert(std::is_same_v<int, seqan3::detail::transformation_trait_or_t<A<int>, void>>);

Attention

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

Helper types

seqan3::detail::transformation_trait_or_t as a shorthand for seqan3::detail::transformation_trait_or::type

transformation_trait_or_t

template<typename type_t , typename default_t >

using seqan3::detail::transformation_trait_or_t = typedef typename transformation_trait_or<type_t, default_t>::type

Helper type of seqan3::detail::transformation_trait_or (transformation_trait shortcut).

See also

seqan3::detail::transformation_trait_or

Variable Documentation

decays_to_ignore_v

template<typename t >

constexpr bool seqan3::detail::decays_to_ignore_v = std::is_same_v<std::remove_cvref_t<t>, ignore_t>

constexpr

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.