depish/cppdraft_translate
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
Files
main
cppdraft_translate/cppdraft/range/iota/view.md
Leonov Artur (Depish) 043225d523 Init
2025-10-25 03:02:53 +03:00

292 lines
12 KiB
Markdown
Raw Permalink Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

[range.iota.view]
# 25 Ranges library [[ranges]](./#ranges)
## 25.6 Range factories [[range.factories]](range.factories#range.iota.view)
### 25.6.4 Iota view [[range.iota]](range.iota#view)
#### 25.6.4.2 Class template iota_view [range.iota.view]
[🔗](#lib:iota_view)
namespace std::ranges {template<class I>concept [*decrementable*](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]") = *see below*; // *exposition only*template<class I>concept [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]") = *see below*; // *exposition only*template<[weakly_incrementable](iterator.concept.winc#concept:weakly_incrementable "24.3.4.4 Concept weakly_­incrementable [iterator.concept.winc]") W, [semiregular](concepts.object#concept:semiregular "18.6 Object concepts [concepts.object]") Bound = unreachable_sentinel_t>requires [*weakly-equality-comparable-with*](concept.equalitycomparable#concept:weakly-equality-comparable-with "18.5.4 Concept equality_­comparable [concept.equalitycomparable]")<W, Bound> && [copyable](concepts.object#concept:copyable "18.6 Object concepts [concepts.object]")<W>class iota_view : public view_interface<iota_view<W, Bound>> {private:// [[range.iota.iterator]](range.iota.iterator "25.6.4.3 Class iota_­view​::​iterator"), class iota_view​::​*iterator*struct *iterator*; // *exposition only*// [[range.iota.sentinel]](range.iota.sentinel "25.6.4.4 Class iota_­view​::​sentinel"), class iota_view​::​*sentinel*struct *sentinel*; // *exposition only* W *value_* = W(); // *exposition only* Bound *bound_* = Bound(); // *exposition only*public: iota_view() requires [default_initializable](concept.default.init#concept:default_initializable "18.4.12 Concept default_­initializable [concept.default.init]")<W> = default; constexpr explicit iota_view(W value); constexpr explicit iota_view(type_identity_t<W> value, type_identity_t<Bound> bound); constexpr explicit iota_view(*iterator* first, *see below* last); constexpr *iterator* begin() const; constexpr auto end() const; constexpr *iterator* end() const requires [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<W, Bound>; constexpr bool empty() const; constexpr auto size() const requires *see below*; }; template<class W, class Bound>requires (!*is-integer-like*<W> || !*is-integer-like*<Bound> ||(*is-signed-integer-like*<W> == *is-signed-integer-like*<Bound>)) iota_view(W, Bound) -> iota_view<W, Bound>;}
[1](#1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2856)
Let *IOTA-DIFF-T*(W) be defined as follows:
- [(1.1)](#1.1)
If W is not an integral type, or
if it is an integral type and sizeof(iter_difference_t<W>) is greater than sizeof(W),
then *IOTA-DIFF-T*(W) denotes iter_difference_t<W>[.](#1.1.sentence-1)
- [(1.2)](#1.2)
Otherwise, *IOTA-DIFF-T*(W) is a signed integer type of width greater than the width of W if such a type exists[.](#1.2.sentence-1)
- [(1.3)](#1.3)
Otherwise, *IOTA-DIFF-T*(W) is an unspecified signed-integer-like type ([[iterator.concept.winc]](iterator.concept.winc "24.3.4.4 Concept weakly_­incrementable"))
of width not less than the width of W[.](#1.3.sentence-1)
[*Note [1](#note-1)*:
It is unspecified
whether this type satisfies [weakly_incrementable](iterator.concept.winc#concept:weakly_incrementable "24.3.4.4 Concept weakly_­incrementable [iterator.concept.winc]")[.](#1.3.sentence-2)
— *end note*]
[2](#2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2878)
The exposition-only [*decrementable*](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]") concept is equivalent to:
[🔗](#concept:decrementable)
`template<class I>
concept [decrementable](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]") = // exposition only
[incrementable](iterator.concept.inc#concept:incrementable "24.3.4.5 Concept incrementable [iterator.concept.inc]")<I> && requires(I i) {
{ --i } -> [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<I&>;
{ i-- } -> [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<I>;
};
`
[3](#3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2890)
When an object is in the domain of both pre- and post-decrement,
the object is said to be [*decrementable*](#def:decrementable)[.](#3.sentence-1)
[4](#4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2894)
Let a and b be equal objects of type I[.](#4.sentence-1)
I models [*decrementable*](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]") only if
- [(4.1)](#4.1)
If a and b are decrementable,
then the following are all true:
* [(4.1.1)](#4.1.1)
addressof(--a) == addressof(a)
* [(4.1.2)](#4.1.2)
bool(a-- == b)
* [(4.1.3)](#4.1.3)
bool(((void)a--, a) == --b)
* [(4.1.4)](#4.1.4)
bool(++(--a) == b)[.](#4.1.sentence-1)
- [(4.2)](#4.2)
If a and b are incrementable,
then bool(--(++a) == b)[.](#4.2.sentence-1)
[5](#5)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2911)
The exposition-only [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]") concept is equivalent to:
[🔗](#concept:advanceable)
`template<class I>
concept [advanceable](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]") = // exposition only
[decrementable](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]")<I> && [totally_ordered](concept.totallyordered#concept:totally_ordered "18.5.5 Concept totally_­ordered [concept.totallyordered]")<I> &&
requires(I i, const I j, const IOTA-DIFF-T(I) n) {
{ i += n } -> [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<I&>;
{ i -= n } -> [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<I&>;
I(j + n);
I(n + j);
I(j - n);
{ j - j } -> [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<IOTA-DIFF-T(I)>;
};
`
Let D be *IOTA-DIFF-T*(I)[.](#sentence-1)
Let a and b be objects of type I such thatb is reachable from a after n applications of ++a,
for some value n of type D[.](#sentence-2)
I models [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]") only if
- (a += n) is equal to b[.](#sentence-1)
- addressof(a += n) is equal to addressof(a)[.](#sentence-1)
- I(a + n) is equal to (a += n)[.](#sentence-1)
- For any two positive values x and y of type D,
if I(a + D(x + y)) is well-defined, then I(a + D(x + y)) is equal to I(I(a + x) + y)[.](#sentence-1)
- I(a + D(0)) is equal to a[.](#sentence-1)
- If I(a + D(n - 1)) is well-defined, then I(a + n) is equal to [](I c) { return ++c; }(I(a + D(n - 1)))[.](#sentence-1)
- (b += -n) is equal to a[.](#sentence-1)
- (b -= n) is equal to a[.](#sentence-1)
- addressof(b -= n) is equal to addressof(b)[.](#sentence-1)
- I(b - n) is equal to (b -= n)[.](#sentence-1)
- D(b - a) is equal to n[.](#sentence-1)
- D(a - b) is equal to D(-n)[.](#sentence-1)
- bool(a <= b) is true[.](#sentence-1)
[🔗](#lib:iota_view,constructor)
`constexpr explicit iota_view(W value);
`
[6](#6)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2959)
*Preconditions*: Bound denotes unreachable_sentinel_t orBound() is reachable from value[.](#6.sentence-1)
When W and Bound model [totally_ordered_with](concept.totallyordered#concept:totally_ordered_with "18.5.5 Concept totally_­ordered [concept.totallyordered]"),
then bool(value <= Bound()) is true[.](#6.sentence-2)
[7](#7)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2966)
*Effects*: Initializes *value_* with value[.](#7.sentence-1)
[🔗](#lib:iota_view,constructor_)
`constexpr explicit iota_view(type_identity_t<W> value, type_identity_t<Bound> bound);
`
[8](#8)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2977)
*Preconditions*: Bound denotes unreachable_sentinel_t orbound is reachable from value[.](#8.sentence-1)
When W and Bound model [totally_ordered_with](concept.totallyordered#concept:totally_ordered_with "18.5.5 Concept totally_­ordered [concept.totallyordered]"),
then bool(value <= bound) is true[.](#8.sentence-2)
[9](#9)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2984)
*Effects*: Initializes *value_* with value and*bound_* with bound[.](#9.sentence-1)
[🔗](#lib:iota_view,constructor__)
`constexpr explicit iota_view(iterator first, see below last);
`
[10](#10)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2996)
*Effects*: Equivalent to:
- [(10.1)](#10.1)
If [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<W, Bound> is true,iota_view(first.*value_*, last.*value_*)[.](#10.1.sentence-1)
- [(10.2)](#10.2)
Otherwise, if Bound denotes unreachable_sentinel_t,iota_view(first.*value_*, last)[.](#10.2.sentence-1)
- [(10.3)](#10.3)
Otherwise, iota_view(first.*value_*, last.*bound_*)[.](#10.3.sentence-1)
[11](#11)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3010)
*Remarks*: The type of last is:
- [(11.1)](#11.1)
If [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<W, Bound> is true, *iterator*[.](#11.1.sentence-1)
- [(11.2)](#11.2)
Otherwise, if Bound denotes unreachable_sentinel_t,Bound[.](#11.2.sentence-1)
- [(11.3)](#11.3)
Otherwise, *sentinel*[.](#11.3.sentence-1)
[🔗](#lib:begin,iota_view)
`constexpr iterator begin() const;
`
[12](#12)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3030)
*Effects*: Equivalent to: return *iterator*{*value_*};
[🔗](#lib:end,iota_view)
`constexpr auto end() const;
`
[13](#13)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3041)
*Effects*: Equivalent to:if constexpr ([same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<Bound, unreachable_sentinel_t>)return unreachable_sentinel;elsereturn *sentinel*{*bound_*};
[🔗](#lib:end,iota_view_)
`constexpr iterator end() const requires [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<W, Bound>;
`
[14](#14)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3058)
*Effects*: Equivalent to: return *iterator*{*bound_*};
[🔗](#lib:empty,iota_view)
`constexpr bool empty() const;
`
[15](#15)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3069)
*Effects*: Equivalent to: return *value_* == *bound_*;
[🔗](#lib:size,iota_view)
`constexpr auto size() const requires see below;
`
[16](#16)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3080)
*Effects*: Equivalent to:if constexpr (*is-integer-like*<W> && *is-integer-like*<Bound>)return (*value_* < 0)? ((*bound_* < 0)? *to-unsigned-like*(-*value_*) - *to-unsigned-like*(-*bound_*): *to-unsigned-like*(*bound_*) + *to-unsigned-like*(-*value_*)): *to-unsigned-like*(*bound_*) - *to-unsigned-like*(*value_*);elsereturn *to-unsigned-like*(*bound_* - *value_*);
[17](#17)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3094)
*Remarks*: The expression in the [*requires-clause*](temp.pre#nt:requires-clause "13.1 Preamble [temp.pre]") is equivalent to:([same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<W, Bound> && [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>) || (*is-integer-like*<W> && *is-integer-like*<Bound>) ||[sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<Bound, W>
Reference in New Issue View Git Blame Copy Permalink