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bug#16048: 24.3.50; String compare surprise
From: |
Eli Zaretskii |
Subject: |
bug#16048: 24.3.50; String compare surprise |
Date: |
Wed, 04 Dec 2013 19:29:30 +0200 |
> From: Josh <josh@foxtail.org>
> Date: Wed, 4 Dec 2013 06:00:46 -0800
> Cc: Michael Albinus <michael.albinus@gmx.de>, 16048@debbugs.gnu.org
>
> On Wed, Dec 4, 2013 at 5:07 AM, Andreas Schwab <schwab@linux-m68k.org>wrote:
>
> > michael.albinus@gmx.de writes:
> >
> > > The following form evals to nil:
> > >
> > > (string-equal "\377" "ΓΏ")
> >
> > "\377" is a unibyte string. When converted to multibyte it yields
> > "\x3fffff".
>
>
> At least as of 24.3, the manual[0] suggests that such a conversion
> should not occur in this case:
And it doesn't occur, indeed:
(multibyte-string-p "\377")
=> nil
> You can also use hexadecimal escape sequences (`\xN') and octal
> escape sequences (`\N') in string constants. *But beware:* If a
> string constant contains hexadecimal or octal escape sequences,
> and these escape sequences all specify unibyte characters (i.e.,
> less than 256), and there are no other literal non-ASCII
> characters or Unicode-style escape sequences in the string, then
> Emacs automatically assumes that it is a unibyte string. That is
> to say, it assumes that all non-ASCII characters occurring in the
> string are 8-bit raw bytes.
>
> [0] (info "(elisp) Non-ASCII in Strings")
Best citation contest? you're on!
-- Function: string= string1 string2
This function returns `t' if the characters of the two strings
match exactly. Symbols are also allowed as arguments, in which
case the symbol names are used. Case is always significant,
regardless of `case-fold-search'.
[...]
For technical reasons, a unibyte and a multibyte string are
`equal' if and only if they contain the same sequence of character
codes and all these codes are either in the range 0 through 127
(ASCII) or 160 through 255 (`eight-bit-graphic'). However, when a
unibyte string is converted to a multibyte string, all characters
with codes in the range 160 through 255 are converted to
characters with higher codes, whereas ASCII characters remain
unchanged. Thus, a unibyte string and its conversion to multibyte
are only `equal' if the string is all ASCII.
Note the last sentence.
- bug#16048: 24.3.50; String compare surprise, michael . albinus, 2013/12/04
- bug#16048: 24.3.50; String compare surprise, Andreas Schwab, 2013/12/04
- bug#16048: 24.3.50; String compare surprise, Michael Albinus, 2013/12/04
- bug#16048: 24.3.50; String compare surprise, Eli Zaretskii, 2013/12/04
- bug#16048: 24.3.50; String compare surprise, Stefan Monnier, 2013/12/04
- bug#16048: 24.3.50; String compare surprise, Michael Albinus, 2013/12/05
- bug#16048: 24.3.50; String compare surprise, Eli Zaretskii, 2013/12/05
- bug#16048: 24.3.50; String compare surprise, Stefan Monnier, 2013/12/05
- bug#16048: 24.3.50; String compare surprise, Eli Zaretskii, 2013/12/05
- bug#16048: 24.3.50; String compare surprise, Michael Albinus, 2013/12/05
- bug#16048: 24.3.50; String compare surprise, Michael Albinus, 2013/12/05