[range.subrange.ctor]

# 25 Ranges library [[ranges]](./#ranges)

## 25.5 Range utilities [[range.utility]](range.utility#range.subrange.ctor)

### 25.5.4 Sub-ranges [[range.subrange]](range.subrange#ctor)

#### 25.5.4.2 Constructors and conversions [range.subrange.ctor]

[🔗](#lib:subrange,constructor)

`constexpr subrange([convertible-to-non-slicing](range.subrange.general#concept:convertible-to-non-slicing "25.5.4.1 General [range.subrange.general]")<I> auto i, S s) requires (!StoreSize);
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2020)

*Preconditions*: [i, s) is a valid range[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2024)

*Effects*: Initializes *begin_* with std​::​move(i) and *end_* withs[.](#2.sentence-1)

[🔗](#lib:subrange,constructor_)

`constexpr subrange([convertible-to-non-slicing](range.subrange.general#concept:convertible-to-non-slicing "25.5.4.1 General [range.subrange.general]")<I> auto i, S s,
                   make-unsigned-like-t<iter_difference_t<I>> n)
  requires (K == subrange_kind::sized);
`

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2038)

*Preconditions*: [i, s) is a valid range, andn == *to-unsigned-like*(ranges​::​distance(i, s)) is true[.](#3.sentence-1)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2044)

*Effects*: Initializes *begin_* with std​::​move(i) and *end_* withs[.](#4.sentence-1)

If *StoreSize* is true, initializes *size_* withn[.](#4.sentence-2)

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2050)

[*Note [1](#note-1)*:

Accepting the length of the range and storing it to later return fromsize() enables subrange to model [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]") even
when it stores an iterator and sentinel that do not model[sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")[.](#5.sentence-1)

— *end note*]

[🔗](#lib:subrange,constructor__)

`template<[different-from](range.utility.helpers#concept:different-from "25.5.2 Helper concepts [range.utility.helpers]")<subrange> R>
  requires [borrowed_range](range.range#concept:borrowed_range "25.4.2 Ranges [range.range]")<R> &&
           [convertible-to-non-slicing](range.subrange.general#concept:convertible-to-non-slicing "25.5.4.1 General [range.subrange.general]")<iterator_t<R>, I> &&
           [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<sentinel_t<R>, S>
constexpr subrange(R&& r) requires (!StoreSize || [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]")<R>);
`

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2069)

*Effects*: Equivalent to:

- [(6.1)](#6.1)

  If *StoreSize* is true,subrange(r, static_cast<decltype(*size_*)>(ranges​::​size(r)))[.](#6.1.sentence-1)

- [(6.2)](#6.2)

  Otherwise, subrange(ranges​::​begin(r), ranges​::​end(r))[.](#6.2.sentence-1)

[🔗](#lib:operator_PairLike,subrange)

`template<[different-from](range.utility.helpers#concept:different-from "25.5.2 Helper concepts [range.utility.helpers]")<subrange> PairLike>
  requires [pair-like-convertible-from](range.subrange.general#concept:pair-like-convertible-from "25.5.4.1 General [range.subrange.general]")<PairLike, const I&, const S&>
constexpr operator PairLike() const;
`

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2087)

*Effects*: Equivalent to: return PairLike(*begin_*, *end_*);