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;Improve documentation of locale-specific string comparison

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* doc/lispref/strings.texi (Text Comparison): Mention the Unicode
collation rules and buffer-local case-tables.
This commit is contained in:
Eli Zaretskii 2022-07-21 09:53:45 +03:00
parent ea44d7ddfc
commit 2b31e667be
1 changed files with 14 additions and 5 deletions
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19
doc/lispref/strings.texi
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@ -564,11 +564,19 @@ equal with respect to collation rules. A collation rule is not only
determined by the lexicographic order of the characters contained in
@var{string1} and @var{string2}, but also further rules about
relations between these characters. Usually, it is defined by the
@var{locale} environment Emacs is running with.
@var{locale} environment Emacs is running with and by the Standard C
library against which Emacs was linked@footnote{
For more information about collation rules and their locale
dependencies, see @uref{https://unicode.org/reports/tr10/, The Unicode
Collation Algorithm}. Some Standard C libraries, such as the
@acronym{GNU} C Library (a.k.a.@: @dfn{glibc}) implement large
portions of the Unicode Collation Algorithm and use the associated
locale data, Common Locale Data Repository, or @acronym{CLDR}.
}.
For example, characters with different coding points but
the same meaning might be considered as equal, like different grave
accent Unicode characters:
For example, characters with different code points but the same
meaning, like different grave accent Unicode characters, might, in
some locales, be considered as equal:
@example
@group
@ -756,7 +764,8 @@ The strings are compared by the numeric values of their characters.
For instance, @var{str1} is considered less than @var{str2} if
its first differing character has a smaller numeric value. If
@var{ignore-case} is non-@code{nil}, characters are converted to
upper-case before comparing them. Unibyte strings are converted to
upper-case, using the current buffer's case-table (@pxref{Case
Tables}), before comparing them. Unibyte strings are converted to
multibyte for comparison (@pxref{Text Representations}), so that a
unibyte string and its conversion to multibyte are always regarded as
equal.