SeqAn3  3.0.3
The Modern C++ library for sequence analysis.
Type List

Provides seqan3::type_list and metaprogramming utilities for working on type lists. More...

+ Collaboration diagram for Type List:

Classes

struct  seqan3::type_list< types >
 Type that contains multiple types. More...
 

Type list traits (return a single type)

template<ptrdiff_t idx, typename list_t >
using seqan3::list_traits::at = typename decltype(detail::at< idx >(list_t{}))::type
 Return the type at given index from the type list. More...
 
template<typename list_t >
using seqan3::list_traits::front = typename decltype(detail::front(list_t{}))::type
 Return the first type from the type list. More...
 
template<typename list_t >
using seqan3::list_traits::back = typename decltype(detail::back(list_t{}))::type
 Return the last type from the type list. More...
 

Type list traits (return a type list)

template<typename ... lists_t>
using seqan3::list_traits::concat = decltype(detail::concat(lists_t{}...))
 Join two seqan3::type_list s into one. More...
 
template<typename list_t >
using seqan3::list_traits::drop_front = decltype(detail::drop_front(list_t{}))
 Return a seqan3::type_list of all the types in the type list, except the first. More...
 
template<ptrdiff_t i, typename list_t >
using seqan3::list_traits::take = typename decltype(detail::split_after< i >(list_t{}))::first_type
 Return a seqan3::type_list of the first n types in the input type list. More...
 
template<ptrdiff_t i, typename list_t >
using seqan3::list_traits::drop = typename decltype(detail::split_after< i >(list_t{}))::second_type
 Return a seqan3::type_list of the types in the input type list, except the first n. More...
 
template<ptrdiff_t i, typename list_t >
using seqan3::list_traits::take_last = drop< size< list_t > - i, list_t >
 Return a seqan3::type_list of the last n types in the input type list. More...
 
template<ptrdiff_t i, typename list_t >
using seqan3::list_traits::drop_last = take< size< list_t > - i, list_t >
 Return a seqan3::type_list of the types the input type list, except the last n. More...
 
template<ptrdiff_t i, typename list_t >
using seqan3::list_traits::split_after = decltype(detail::split_after< i >(list_t{}))
 Split a seqan3::type_list into two parts returned as a pair of seqan3::type_list. More...
 
template<template< typename > typename trait_t, typename list_t >
using seqan3::list_traits::transform = decltype(detail::transform< trait_t >(list_t{}))
 Apply a transformation trait to every type in the list and return a seqan3::type_list of the results. More...
 
template<typename replace_t , std::ptrdiff_t i, typename list_t >
using seqan3::list_traits::replace_at = decltype(detail::replace_at< replace_t, i >(list_t{}))
 Replace the type at the given index with the given type. More...
 

Type list traits (return a value)

template<typename ... pack_t>
constexpr size_t seqan3::list_traits::size< type_list< pack_t... > > = sizeof...(pack_t)
 The size of a type list. More...
 
template<typename query_t , typename ... pack_t>
constexpr ptrdiff_t seqan3::list_traits::count< query_t, type_list< pack_t... > >
 Count the occurrences of a type in a type list. More...
 
template<typename query_t , typename ... pack_t>
constexpr ptrdiff_t seqan3::list_traits::find< query_t, type_list< pack_t... > >
 Get the index of the first occurrence of a type in a type list. More...
 
template<template< typename > typename pred_t, typename ... pack_t>
constexpr ptrdiff_t seqan3::list_traits::find_if< pred_t, type_list< pack_t... > >
 Get the index of the first type in a type list that satisfies the given predicate. More...
 
template<typename query_t , typename list_t >
constexpr bool seqan3::list_traits::contains = (find<query_t, list_t> != -1)
 Whether a type occurs in a type list or not. More...
 

Detailed Description

Provides seqan3::type_list and metaprogramming utilities for working on type lists.

All traits on type lists are defined in the header <seqan3/utility/type_list/traits.hpp>.

Typedef Documentation

◆ at

template<ptrdiff_t idx, typename list_t >
using seqan3::list_traits::at = typedef typename decltype(detail::at<idx>(list_t{}))::type

Return the type at given index from the type list.

Template Parameters
idxThe index; must be smaller than the size of the type list.
list_tThe type_list.

Negative indexes are supported (e.g. at<-1, type_list<int, double, bool &>> is bool &).

(Compile-time) Complexity

  • Number of template instantiations: O(n)
  • Other operations: O(n)
int main()
{
// Look at the 2nd element.
static_assert(std::same_as<float, seqan3::list_traits::at<1, list_t>>);
// Look at the last element.
static_assert(std::same_as<double, seqan3::list_traits::at<-1, list_t>>);
}
typename decltype(detail::at< idx >(list_t{}))::type at
Return the type at given index from the type list.
Definition: traits.hpp:233
Type that contains multiple types.
Definition: type_list.hpp:29
Provides traits for seqan3::type_list.

◆ back

template<typename list_t >
using seqan3::list_traits::back = typedef typename decltype(detail::back(list_t{}))::type

Return the last type from the type list.

Template Parameters
list_tThe type list.

(Compile-time) Complexity

  • Number of template instantiations: O(n) (possibly O(1))
  • Other operations: O(1)

Notably faster than seqan3::pack_traits::at<size<pack...> - 1, pack...> (no recursive template instantiations).

int main()
{
// Access the last value (float) with seqan3::list_traits::back
static_assert(std::same_as<float, seqan3::list_traits::back<list_t>>);
}
typename decltype(detail::back(list_t{}))::type back
Return the last type from the type list.
Definition: traits.hpp:274

◆ concat

template<typename ... lists_t>
using seqan3::list_traits::concat = typedef decltype(detail::concat(lists_t{}...))

Join two seqan3::type_list s into one.

Template Parameters
list1_tThe first (input) type list.
list2_tThe second (input) type list.

(Compile-time) Complexity

  • Number of template instantiations: O(n) in the number of type lists
  • Other operations: O(n) in the number of type lists

Complexity is independent of the number of types in each list.

int main()
{
using list_t3 = seqan3::type_list<int, int>;
}
decltype(detail::concat(lists_t{}...)) concat
Join two seqan3::type_list s into one.
Definition: traits.hpp:302

◆ drop

template<ptrdiff_t i, typename list_t >
using seqan3::list_traits::drop = typedef typename decltype(detail::split_after<i>(list_t{}))::second_type

Return a seqan3::type_list of the types in the input type list, except the first n.

Template Parameters
iThe amount to drop; must be >= 0 and <= the size of the input type list.
list_tThe (input) type list.

(Compile-time) Complexity

  • Number of template instantiations: O(n)
  • Other operations: O(n)
int main()
{
// Drop the first two types in list_t.
}
typename decltype(detail::split_after< i >(list_t{}))::second_type drop
Return a seqan3::type_list of the types in the input type list, except the first n.
Definition: traits.hpp:361

◆ drop_front

template<typename list_t >
using seqan3::list_traits::drop_front = typedef decltype(detail::drop_front(list_t{}))

Return a seqan3::type_list of all the types in the type list, except the first.

Template Parameters
list_tThe (input) type list.

(Compile-time) Complexity

  • Number of template instantiations: O(1)
  • Other operations: O(1)
int main()
{
}
decltype(detail::drop_front(list_t{})) drop_front
Return a seqan3::type_list of all the types in the type list, except the first.
Definition: traits.hpp:321

◆ drop_last

template<ptrdiff_t i, typename list_t >
using seqan3::list_traits::drop_last = typedef take<size<list_t> - i, list_t>

Return a seqan3::type_list of the types the input type list, except the last n.

Template Parameters
iThe amount to drop; must be >= 0 and <= the size of the input type list.
list_tThe (input) type list.

(Compile-time) Complexity

  • Number of template instantiations: O(n)
  • Other operations: O(n)
int main()
{
// Drop the last two types in list_t.
}
take< size< list_t > - i, list_t > drop_last
Return a seqan3::type_list of the types the input type list, except the last n.
Definition: traits.hpp:401

◆ front

template<typename list_t >
using seqan3::list_traits::front = typedef typename decltype(detail::front(list_t{}))::type

Return the first type from the type list.

Template Parameters
list_tThe type list.

(Compile-time) Complexity

  • Number of template instantiations: O(1)
  • Other operations: O(1)
int main()
{
static_assert(std::same_as<int, seqan3::list_traits::front<list_t>>); // Check if the first value is int.
}
typename decltype(detail::front(list_t{}))::type front
Return the first type from the type list.
Definition: traits.hpp:252

◆ replace_at

template<typename replace_t , std::ptrdiff_t i, typename list_t >
using seqan3::list_traits::replace_at = typedef decltype(detail::replace_at<replace_t, i>(list_t{}))

Replace the type at the given index with the given type.

Template Parameters
replace_tThe type to replace the old type with.
iThe index of the type to be replaced.
list_tThe (input) type list.

(Compile-time) Complexity

  • Number of template instantiations: O(n)
  • Other operations: O(n)
int main()
{
// Replace the second element with int.
}
decltype(detail::replace_at< replace_t, i >(list_t{})) replace_at
Replace the type at the given index with the given type.
Definition: traits.hpp:465

◆ split_after

template<ptrdiff_t i, typename list_t >
using seqan3::list_traits::split_after = typedef decltype(detail::split_after<i>(list_t{}))

Split a seqan3::type_list into two parts returned as a pair of seqan3::type_list.

Template Parameters
iThe number of elements after which to split; must be >= 0 and <= the size of the input type list.
list_tThe (input) type list.

(Compile-time) Complexity

  • Number of template instantiations: O(n)
  • Other operations: O(n)
int main()
{
// Drop the last two types in list_t.
}

◆ take

template<ptrdiff_t i, typename list_t >
using seqan3::list_traits::take = typedef typename decltype(detail::split_after<i>(list_t{}))::first_type

Return a seqan3::type_list of the first n types in the input type list.

Template Parameters
iThe target size; must be >= 0 and <= the size of the input type list.
list_tThe (input) type list.

(Compile-time) Complexity

  • Number of template instantiations: O(n)
  • Other operations: O(n)
int main()
{
// Take the first two types in list_t.
}
typename decltype(detail::split_after< i >(list_t{}))::first_type take
Return a seqan3::type_list of the first n types in the input type list.
Definition: traits.hpp:341

◆ take_last

template<ptrdiff_t i, typename list_t >
using seqan3::list_traits::take_last = typedef drop<size<list_t> - i, list_t>

Return a seqan3::type_list of the last n types in the input type list.

Template Parameters
iThe target size; must be >= 0 and <= the size of the input type list.
list_tThe (input) type list.

(Compile-time) Complexity

  • Number of template instantiations: O(n)
  • Other operations: O(n)
int main()
{
// Take the last two types in list_t.
}
drop< size< list_t > - i, list_t > take_last
Return a seqan3::type_list of the last n types in the input type list.
Definition: traits.hpp:381

◆ transform

template<template< typename > typename trait_t, typename list_t >
using seqan3::list_traits::transform = typedef decltype(detail::transform<trait_t>(list_t{}))

Apply a transformation trait to every type in the list and return a seqan3::type_list of the results.

Template Parameters
trait_tThe trait to transform, must be an alias template, e.g. a transformation trait shortcut.
list_tThe (input) type list.

The transformation trait given as first argument must be an alias template, e.g. std::type_identity_t, not std::type_identity. The alias must take exactly one argument and be defined for all types in the input list.

(Compile-time) Complexity

  • Number of template instantiations: O(n)
  • Other operations: O(n)
#include <list>
#include <vector>
int main()
{
// Transform the types into reference types.
}
Provides various transformation traits used by the range module.
decltype(detail::transform< trait_t >(list_t{})) transform
Apply a transformation trait to every type in the list and return a seqan3::type_list of the results.
Definition: traits.hpp:444

Variable Documentation

◆ contains

template<typename query_t , typename list_t >
constexpr bool seqan3::list_traits::contains = (find<query_t, list_t> != -1)
inlineconstexpr

Whether a type occurs in a type list or not.

Template Parameters
query_tThe type you are searching for.
pack_tThe type pack.
Returns
true or false.

(Compile-time) Complexity

  • Number of template instantiations: O(1)
  • Other operations: O(n), possibly == i, where i is the index of the first occurrence
int main()
{
// Double is not in the pack so find returns -1. However, bool is in the pack so find will return 2.
static_assert(seqan3::pack_traits::find<double, int, float, bool> == -1);
static_assert(seqan3::pack_traits::find<bool, int, float, bool> == 2);
}
Provides various traits for template packs.
int main()
{
static_assert(seqan3::list_traits::contains<double, list_t> == false); // Is type double in type_list list_t?
static_assert(seqan3::list_traits::contains<float, list_t> == true); // Is type float in type_list list_t?
}

◆ count< query_t, type_list< pack_t... > >

template<typename query_t , typename ... pack_t>
constexpr ptrdiff_t seqan3::list_traits::count< query_t, type_list< pack_t... > >
inlineconstexpr
Initial value:
=
seqan3::pack_traits::count<query_t, pack_t...>
constexpr ptrdiff_t count
Count the occurrences of a type in a pack.
Definition: traits.hpp:169

Count the occurrences of a type in a type list.

Template Parameters
query_tThe type you are searching for.
pack_tThe type pack.
Returns
The number of occurrences of the query_t in pack_t.

(Compile-time) Complexity

  • Number of template instantiations: O(1)
  • Other operations: O(n)
int main()
{
// Count the number of type int in the pack.
static_assert(seqan3::pack_traits::count<int, int, float, bool, int> == 2);
}
int main()
{
// Count the number of type int in list_t.
static_assert(seqan3::list_traits::count<int, list_t> == 2);
}

◆ find< query_t, type_list< pack_t... > >

template<typename query_t , typename ... pack_t>
constexpr ptrdiff_t seqan3::list_traits::find< query_t, type_list< pack_t... > >
inlineconstexpr
Initial value:
=
seqan3::pack_traits::detail::find<query_t, pack_t...>()

Get the index of the first occurrence of a type in a type list.

Template Parameters
query_tThe type you are searching for.
pack_tThe type pack.
Returns
The position of the first occurrence of query_t in pack_t or -1 if it is not contained.

(Compile-time) Complexity

  • Number of template instantiations: O(1)
  • Other operations: O(n), possibly == i, where i is the return value
int main()
{
// Double is not in the pack so find returns -1. However, bool is in the pack so find will return 2.
static_assert(seqan3::pack_traits::find<double, int, float, bool> == -1);
static_assert(seqan3::pack_traits::find<bool, int, float, bool> == 2);
}
int main()
{
// Double is not in list_t so find returns -1. However, bool is in the type list so find will return 2.
static_assert(seqan3::list_traits::find<double, list_t> == -1);
static_assert(seqan3::list_traits::find<bool, list_t> == 2);
}

◆ find_if< pred_t, type_list< pack_t... > >

template<template< typename > typename pred_t, typename ... pack_t>
constexpr ptrdiff_t seqan3::list_traits::find_if< pred_t, type_list< pack_t... > >
inlineconstexpr
Initial value:
=
seqan3::pack_traits::detail::find_if<pred_t, pack_t...>()

Get the index of the first type in a type list that satisfies the given predicate.

Template Parameters
pred_tThe predicate that is being evaluated (a class template).
pack_tThe type pack.
Returns
The index or -1 if no types match.

Note that the predicate must be given as a type template (variable templates cannot be passed as template arguments unfortunately). This means e.g. find_if<std::is_integral, float, double, int, float> (not std::is_integral_v!).

(Compile-time) Complexity

  • Number of template instantiations: O(n), possibly == i, where i is the return value
  • Other operations: O(n), possibly == i, where i is the return value

    Only the predicate is instantiated.

int main()
{
// None of the types in t is a pointer so find_if returns -1. However, int and bool are both integral,
// so find_if returns 0 for the first occurrence.
static_assert(seqan3::pack_traits::find_if<std::is_pointer, int, float, double> == -1);
static_assert(seqan3::pack_traits::find_if<std::is_integral, int, float, double> == 0);
}
int main()
{
// Double is not in list_t so find returns -1. However, bool is in the type list so find will return 2.
static_assert(seqan3::list_traits::find<double, list_t> == -1);
static_assert(seqan3::list_traits::find<bool, list_t> == 2);
}

◆ size< type_list< pack_t... > >

template<typename ... pack_t>
constexpr size_t seqan3::list_traits::size< type_list< pack_t... > > = sizeof...(pack_t)
inlineconstexpr

The size of a type list.

Template Parameters
pack_tThe type pack.
Returns
sizeof...(pack_t)

(Compile-time) Complexity

  • Number of template instantiations: O(1)
  • Other operations: O(1)
int main()
{
// Get the size of the pack.
static_assert(seqan3::pack_traits::size<int, float, bool, int> == 4);
}
int main()
{
static_assert(seqan3::list_traits::size<list_t> == 4);
}