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Document RangeFrom patterns #900

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Merged
merged 5 commits into from
Sep 17, 2021
Merged

Document RangeFrom patterns #900

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d845bc3
Add RangeFrom patterns
workingjubilee Nov 9, 2020
abcacb2
More formal writing and links
workingjubilee Feb 25, 2021
51fab18
Offer example
workingjubilee Apr 6, 2021
da75d92
add spacing in src/patterns.md
workingjubilee Aug 3, 2021
76ed5db
Update with slice pattern restrictions
workingjubilee Sep 12, 2021
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Update with slice pattern restrictions
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@workingjubilee
workingjubilee committed Sep 16, 2021
commit 76ed5db1e1783e8ab2642e6c69f596381126052d
22 changes: 17 additions & 5 deletions src/patterns.md
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Expand Up @@ -10,7 +10,6 @@
>    | [_IdentifierPattern_]\
>    | [_WildcardPattern_]\
>    | [_RestPattern_]\
>    | [_ObsoleteRangePattern_]\
>    | [_ReferencePattern_]\
>    | [_StructPattern_]\
>    | [_TupleStructPattern_]\
Expand Down Expand Up @@ -401,7 +400,14 @@ match tuple {

> **<sup>Syntax</sup>**\
> _RangePattern_ :\
> &nbsp;&nbsp; &nbsp;&nbsp; _RangePatternBound_ `..=` _RangePatternBound_\
> &nbsp;&nbsp; &nbsp;&nbsp; _InclusiveRangePattern_\
> &nbsp;&nbsp; | _HalfOpenRangePattern_\
> &nbsp;&nbsp; | _ObsoleteRangePattern_
>
> _InclusiveRangePattern_ :\
> &nbsp;&nbsp; &nbsp;&nbsp; _RangePatternBound_ `..=` _RangePatternBound_
>
> _HalfOpenRangePattern_ :\
> &nbsp;&nbsp; | _RangePatternBound_ `..`
>
> _ObsoleteRangePattern_ :\
Expand All @@ -421,12 +427,14 @@ it matches all the values between and including both of its bounds. A range patt
half-open is written with a lower bound but not an upper bound, and matches any value equal to
or greater than the specified lower bound.

For example, a pattern `'m'..='p'` will match only the values `'m'`, `'n'`, `'o'`, and `'p'`. The
For example, a pattern `'m'..='p'` will match only the values `'m'`, `'n'`, `'o'`, and `'p'`. For an integer the
pattern `1..` will match 9, or 9001, or 9007199254740991 (if it is of an appropriate size), but
not 0 or negative numbers for signed integers. The bounds can be literals or paths that point
not 0, and not negative numbers for signed integers. The bounds can be literals or paths that point
to constant values.

A pattern a `..=` b must always have a &le; b. It is an error to have a range pattern
A half-open range pattern in the style `a..` cannot be used to match within the context of a slice.

A pattern `a..=b` must always have a &le; b. It is an error to have a range pattern
`10..=0`, for example.

The `...` syntax is kept for backwards compatibility.
Expand Down Expand Up @@ -734,6 +742,10 @@ is irrefutable. When matching a slice, it is irrefutable only in the form with
a single `..` [rest pattern](#rest-patterns) or [identifier
pattern](#identifier-patterns) with the `..` rest pattern as a subpattern.

Within a slice, a half-open range pattern like `a..` must be enclosed in parentheses,
as in `(a..)`, to clarify it is intended to match a single value.
A future version of Rust may give the non-parenthesized version an alternate meaning.

## Path patterns

> **<sup>Syntax</sup>**\
Expand Down