diff options
Diffstat (limited to 'pod')
| -rw-r--r-- | pod/perlop.pod | 86 |
1 files changed, 61 insertions, 25 deletions
diff --git a/pod/perlop.pod b/pod/perlop.pod index 6409f9da25..c51afc3af9 100644 --- a/pod/perlop.pod +++ b/pod/perlop.pod @@ -1019,40 +1019,76 @@ and in transliterations. X<\t> X<\n> X<\r> X<\f> X<\b> X<\a> X<\e> X<\x> X<\0> X<\c> X<\N> X<\N{}> Sequence Note Description - \t tab (HT, TAB) - \n newline (NL) - \r return (CR) - \f form feed (FF) - \b backspace (BS) - \a alarm (bell) (BEL) - \e escape (ESC) - \x{263a} [1] hex char (example: SMILEY) - \x1b [2] narrow hex char (example: ESC) + \t tab (HT, TAB) + \n newline (NL) + \r return (CR) + \f form feed (FF) + \b backspace (BS) + \a alarm (bell) (BEL) + \e escape (ESC) + \x{263a} [1] hex char (example: SMILEY) + \x1b [2] restricted hex char (example: ESC) \N{name} [3] named Unicode character - \N{U+263D} [4] Unicode character (example: FIRST QUARTER MOON) - \c[ [5] control char (example: chr(27)) - \033 [6] octal char (example: ESC) + \N{U+263D} [4] Unicode character (example: FIRST QUARTER MOON) + \c[ [5] control char (example: chr(27)) + \033 [6] octal char (example: ESC) =over 4 =item [1] -The result is the character whose ordinal is the hexadecimal number between the -braces. If something other than a hexadecimal digit is encountered, it and -everything following it up to the closing brace are discarded, and if warnings -are enabled, a warning is raised. The leading digits that are hex then -comprise the entire number. If the first thing after the opening brace is not -a hex digit, the generated character is the NULL character. C<\x{}> is the -NULL character with no warning given. +The result is the character whose ordinal is the hexadecimal number between +the braces. If the ordinal is 0x100 and above, the character will be the +Unicode character corresponding to the ordinal. If the ordinal is between +0 and 0xFF, the rules for which character it represents are the same as for +L<restricted hex chars|/[2]>. + +Only hexadecimal digits are valid between the braces. If an invalid +character is encountered, a warning will be issued and the invalid +character and all subsequent characters (valid or invalid) within the +braces will be discarded. + +If there are no valid digits between the braces, the generated character is +the NULL character (C<\x{00}>). However, an explicit empty brace (C<\x{}>) +will not cause a warning. =item [2] -The result is the character whose ordinal is the given two-digit hexadecimal -number. But, if I<H> is a hex digit and I<G> is not, then C<\xI<HG>...> is the -same as C<\x0I<HG>...>, and C<\xI<G>...> is the same thing as C<\x00I<G>...>. -In both cases, the result is two characters, and if warnings are enabled, a -misleading warning message is raised that I<G> is ignored, when in fact it is -used. Note that in the second case, the first character currently is a NULL. +The result is a single-byte character whose ordinal is in the range 0x00 to +0xFF. + +Only hexadecimal digits are valid following C<\x>. When C<\x> is followed +by less than two valid digits, any valid digits will be zero-padded. This +means that C<\x7> will be interpreted as C<\x07> and C<\x> alone will be +interpreted as C<\x00>. Except at the end of a string, having less than +two valid digits will result in a warning. Note that while the warning +says the illegal character is ignored, it is only ignored as part of the +escape and will still be used as the subsequent character in the string. +For example: + + Original Result Warns? + "\x7" "\x07" no + "\x" "\x00" no + "\x7q" "\x07q" yes + "\xq" "\x00q" yes + +The B<run-time> interpretation of single-byte characters depends on the +platform and on pragmata in effect. On EBCDIC platforms the character is +treated as native to the platform's code page. On other platforms, the +representation and semantics (sort order and which characters are upper +case, lower case, digit, non-digit, etc.) depends on the current +L<S<C<locale>>|perllocale> settings at run-time. + +However, when L<C<S<use feature 'unicode_strings'>>|feature> is in effect +and both L<C<S<use bytes>>|bytes> and L<C<S<use locale>>|locale> are not, +characters from 0x80 to 0xff are treated as Unicode code points from +the Latin-1 Supplement block. + +Note that the locale semantics of single-byte characters in a regular +expression are determined when the regular expression is compiled, not when +the regular expression is used. When a regular expression is interpolated +into another regular expression -- any prior semantics are ignored and only +current locale matters for the resulting regular expression. =item [3] |