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Re^3: How to reverse a (Unicode) stringby Jim (Deacon)
|on Jan 31, 2011 at 08:10 UTC||Need Help??|
The documentation of Perl's reverse function states: "In scalar context, [the reverse function] ... returns a string value with all characters in the opposite order."
No. It doesn't know anything about Unicode and there's no requirement for the string to be Unicode text.
The documentation is quite clear: In scalar context, the reverse function operates on strings. If the string is Unicode, it reverses Unicode code points. If the string is in some single-byte character encoding such as ISO 8859-1 (Latin 1), then it reverses those characters. It's really very straightforward.
You're once again trying to make some esoteric point about the distinction between strings and bytes, and what is Unicode and what is not Unicode. But your peculiar, persistent point isn't relevant here.
Nothing in my post is incorrect or inaccurate, yet the supercilious tone of your response wrongly implies that something is incorrect. The topic of this discussion is Unicode text, so of course I'm talking about Unicode text in it.
In my experience, "character" is the constituent element of a string, and never a grapheme except by happenstance. Let's just say there is no such consensus.
What is a character in a language is well-understood and rarely, if ever, subject to debate. In the case of Unicode, "character" is well-defined, too: It's a "grapheme." It's as simple as that. Read the Unicode Standard.
There are four characters in the word "Café", not five. When you arrange the four characters in the opposite order, you get "éfaC". This fact is the very basis of this tutorial and discussion.
No. reverse provides a vital string operation. It should not assume the string is Unicode text.
Your insistence that there's a difference between "string" and "text" may have some strange basis in the arcane details of the internals of Perl, but it has no relevance to this discussion. The whole premise of this discussion is that we're trying to reverse Unicode strings (Unicode text). And the salient point about Perl's reverse function is that it fails to reverse properly an infinite number of possible Unicode strings.
Reversing text is also a useful function, but it is not provided by reverse.
This is a bizarre and incomprehensible statement.
What's the difference between a "string" and "text" to someone writing a Perl program?
Explain why you think this…
use utf8; binmode STDOUT, ':encoding(UTF-8)'; my $Moonshine = "Rươòu ðêì"; my $enihsnooM = reverse $Moonshine; print "$Moonshine\n"; print "$enihsnooM\n";
…should produce different output than this…
use utf8; binmode STDOUT, ':encoding(UTF-8)'; my $Moonshine = "Rươòu ðêì"; my $enihsnooM = join '', reverse $Moonshine =~ m/\X/g; print "$Moonshine\n"; print "$enihsnooM\n";