B<NOTE>: This feature is new in Perl 5.004, and does not apply unless an
application specifically requests it - see L<Backward compatibility>.
+The one exception is that write() now B<always> uses the current locale
+- see L<"NOTES">.
=head1 PREPARING TO USE LOCALES
$equal_in_locale will be true if the collation locale specifies a
dictionary-like ordering which ignores space characters completely, and
-which folds case. Alternatively, you can use this idiom:
-
- use locale;
- $s_a = "space and case ignored";
- $s_b = "SpaceAndCaseIgnored";
- $equal_in_locale = $s_a ge $s_b && $s_a le $s_b;
-
-which works because neither C<ne> nor C<ge> falls back to doing a
-byte-by-byte comparison when the operands are equal according to the
-locale. The idiom may be less efficient than using strcoll(), but,
-unlike that function, it is not confused by strings containing embedded
-nulls.
+which folds case.
If you have a single string which you want to check for "equality in
locale" against several others, you might think you could gain a little
magic (see L<perlguts/Magic>) creates the transformed version of a
string the first time it's needed in a comparison, then keeps it around
in case it's needed again. An example rewritten the easy way with
-C<cmp> runs just about as fast. It also copes with null characters
+C<cmp> runs just about as fast. It also copes with null characters
embedded in strings; if you call strxfrm() directly, it treats the first
-null it finds as a terminator. In short, don't call strxfrm() directly:
-let Perl do it for you.
+null it finds as a terminator. And don't expect the transformed strings
+it produces to be portable across systems - or even from one revision
+of your operating system to the next. In short, don't call strxfrm()
+directly: let Perl do it for you.
Note: C<use locale> isn't shown in some of these examples, as it isn't
needed: strcoll() and strxfrm() exist only to generate locale-dependent
setting, characters like 'E<aelig>', 'E<eth>', 'E<szlig>', and
'E<oslash>' may be understood as C<\w> characters.
-C<LC_CTYPE> also affects the POSIX character-class test functions -
+The C<LC_CTYPE> locale also provides the map used in translating
+characters between lower- and upper-case. This affects the case-mapping
+functions - lc(), lcfirst, uc() and ucfirst(); case-mapping
+interpolation with C<\l>, C<\L>, C<\u> or <\U> in double-quoted strings
+and in C<s///> substitutions; and case-independent regular expression
+pattern matching using the C<i> modifier.
+
+Finally, C<LC_CTYPE> affects the POSIX character-class test functions -
isalpha(), islower() and so on. For example, if you move from the "C"
locale to a 7-bit Scandinavian one, you may find - possibly to your
surprise - that "|" moves from the ispunct() class to isalpha().
=item *
+String interpolation with case-mapping, as in, say, C<$dest =
+"C:\U$name.$ext">, may produce dangerous results if a bogus LC_CTYPE
+case-mapping table is in effect.
+
+=item *
+
If the decimal point character in the C<LC_NUMERIC> locale is
surreptitiously changed from a dot to a comma, C<sprintf("%g",
0.123456e3)> produces a string result of "123,456". Many people would
Scalar true/false (or less/equal/greater) result is never tainted.
+=item B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u> or <\U>)
+
+Result string containing interpolated material is tainted if
+C<use locale> is in effect.
+
=item B<Matching operator> (C<m//>):
Scalar true/false result never tainted.
Subpatterns, either delivered as an array-context result, or as $1 etc.
are tainted if C<use locale> is in effect, and the subpattern regular
-expression contains C<\w> (to match an alphanumeric character). The
-matched pattern variable, $&, is also tainted if C<use locale> is in
-effect, and the regular expression contains C<\w>.
+expression contains C<\w> (to match an alphanumeric character), C<\W>
+(non-alphanumeric character), C<\s> (white-space character), or C<\S>
+(non white-space character). The matched pattern variable, $&, $`
+(pre-match), $' (post-match), and $+ (last match) are also tainted if
+C<use locale> is in effect and the regular expression contains C<\w>,
+C<\W>, C<\s>, or C<\S>.
=item B<Substitution operator> (C<s///>):
-Has the same behavior as the match operator. When C<use locale> is
-in effect, he left operand of C<=~> will become tainted if it is
-modified as a result of a substitution based on a regular expression
-match involving C<\w>.
+Has the same behavior as the match operator. Also, the left
+operand of C<=~> becomes tainted when C<use locale> in effect,
+if it is modified as a result of a substitution based on a regular
+expression match involving C<\w>, C<\W>, C<\s>, or C<\S>; or of
+case-mapping with C<\l>, C<\L>,C<\u> or <\U>.
=item B<In-memory formatting function> (sprintf()):
and the locale.) These downsides are dictated more by the operating
system's implementation of the locale system than by Perl.
+=head2 write() and LC_NUMERIC
+
+Formats are the only part of Perl which unconditionally use information
+from a program's locale; if a program's environment specifies an
+LC_NUMERIC locale, it is always used to specify the decimal point
+character in formatted output. Formatted output cannot be controlled by
+C<use locale> because the pragma is tied to the block structure of the
+program, and, for historical reasons, formats exist outside that block
+structure.
+
=head2 Freely available locale definitions
There is a large collection of locale definitions at
Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic
Dunlop, assisted by the perl5-porters.
-Last update: Tue Dec 24 16:43:11 EST 1996
+Last update: Wed Jan 22 11:04:58 EST 1997
projects / p5sagit/p5-mst-13.2.git / blobdiff