selection of C<-W> flags (see cflags.SH).
Also study L<perlport> carefully to avoid any bad assumptions about the
-operating system, filesystems, and so forth.
+operating system, filesystems, character set, and so forth.
You may once in a while try a "make microperl" to see whether we can
still compile Perl with just the bare minimum of interfaces. (See
Perl can compile and run under EBCDIC platforms. See L<perlebcdic>.
This is transparent for the most part, but because the character sets
differ, you shouldn't use numeric (decimal, octal, nor hex) constants
-to refer to characters. You can safely say 'A', but not 0x41. You can
-safely say '\n', but not \012. If a character doesn't have a trivial
-input form, you should add it to the list in
-F<regen/unicode_constants.pl>, and have Perl create #defines for you,
+to refer to characters. You can safely say C<'A'>, but not C<0x41>.
+You can safely say C<'\n'>, but not C<\012>. However, you can use
+macros defined in F<utf8.h> to specify any code point portably.
+C<LATIN1_TO_NATIVE(0xDF)> is going to be the code point that means
+LATIN SMALL LETTER SHARP S on whatever platform you are running on (on
+ASCII platforms it compiles without adding any extra code, so there is
+zero performance hit on those). The acceptable inputs to
+C<LATIN1_TO_NATIVE> are from C<0x00> through C<0xFF>. If your input
+isn't guaranteed to be in that range, use C<UNICODE_TO_NATIVE> instead.
+C<NATIVE_TO_LATIN1> and C<NATIVE_TO_UNICODE> translate the opposite
+direction.
+
+If you need the string representation of a character that doesn't have a
+mnemonic name in C, you should add it to the list in
+F<regen/unicode_constants.pl>, and have Perl create C<#define>s for you,
based on the current platform.
+Note that the C<isI<FOO>> and C<toI<FOO>> macros in F<handy.h> work
+properly on native code points and strings.
+
Also, the range 'A' - 'Z' in ASCII is an unbroken sequence of 26 upper
case alphabetic characters. That is not true in EBCDIC. Nor for 'a' to
'z'. But '0' - '9' is an unbroken range in both systems. Don't assume
UTF-8 and UTF-EBCDIC are two different encodings used to represent
Unicode code points as sequences of bytes. Macros with the same names
-(but different definitions) in C<utf8.h> and C<utfebcdic.h> are used to
+(but different definitions) in F<utf8.h> and F<utfebcdic.h> are used to
allow the calling code to think that there is only one such encoding.
This is almost always referred to as C<utf8>, but it means the EBCDIC
version as well. Again, comments in the code may well be wrong even if
-the code itself is right. For example, the concept of C<invariant
+the code itself is right. For example, the concept of UTF-8 C<invariant
characters> differs between ASCII and EBCDIC. On ASCII platforms, only
characters that do not have the high-order bit set (i.e. whose ordinals
are strict ASCII, 0 - 127) are invariant, and the documentation and
ASCII is a 7 bit encoding, but bytes have 8 bits in them. The 128 extra
characters have different meanings depending on the locale. Absent a
locale, currently these extra characters are generally considered to be
-unassigned, and this has presented some problems. This is being changed
-starting in 5.12 so that these characters will be considered to be
-Latin-1 (ISO-8859-1).
+unassigned, and this has presented some problems. This has being
+changed starting in 5.12 so that these characters can be considered to
+be Latin-1 (ISO-8859-1).
=item *
https://perl5.git.perl.org / perl5.git / blobdiff