GNU bug report logs - #23902
25.1.50; Strange warning on string-collate-equalp's docstring

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From: oscarfv <at> telefonica.net (Óscar Fuentes)
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: michael_heerdegen <at> web.de, Glenn Morris <rgm <at> gnu.org>, 23902 <at> debbugs.gnu.org
Subject: bug#23902: 25.1.50; Strange warning on string-collate-equalp's docstring
Date: Sat, 09 Jul 2016 23:36:37 +0200

Eli Zaretskii <eliz <at> gnu.org> writes:

> But they can reason this way instead:
>
> "I want to compare two file names.
> Collation is a way to compare strings, for example the man page for
> strcoll says the function returns zero if one string is equal to the
> other.
> And Emacs just learned how to use collation to compare strings, it
> has this great new function string-collate-equalp.
> Therefore, let's use string-collate-equalp for comparing two file
> names."

This implies that the user knows about string comparisons with collation
but he is a complete ignoramus about file systems. A bit unrealistic.

Anyway, saying "don't use this for comparing file names" is cryptic.
Mentioning file-equal-p would be helpful if you insist on mentioning
file names on the docstring of string-collate-equalp.

>> And suppose I have two strings, and want to know if they are equal,
>> respecting my locale's convention about characters that are not
>> literally identical, but have the same meaning. I should use
>> string-collate-equalp for this. This is true whether the strings
>> represent the names of elephants in a zoo, or files on a disk.
>
> And that is exactly the fallacy that the note warns against.  Because
> filesystems don't compare as equal characters that have the same
> meaning, they compare bytes in a byte stream that is the file name in
> its raw byte form, as recorded on disk.

I think that Glenn is saying that you can compare file names for other
purposes than knowing if they name the same file.

Maybe the user wishes to find a file with a given name, modulo
collation. Search for "tu.txt" and find "tú.txt".

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