From: Brian Candler <b.candler@...>
Date: 2010-01-14T03:25:18+09:00
Subject: Re: Ruby Regex

Marnen Laibow-Koser wrote:
> The problem is that Ruby "helpfully" does another level of 
> escaping

It's necessary because it lets you use sequences like \n in 
double-quoted strings, and \" if you want a double-quote, and \#{expr} 
if you want literally # { expr } rather than interpolation.

> so that "\\&" is equivaIent to "\&", whereas it should simply 
> take the escape at face value and consider it equivalent to the two 
> characters \ and &.

Which is what happens in single-quoted strings. But you can't put any 
control character sequences like \n in those.

> For real fun, try concatenating two strings, the first of which ends in 
> a backslash.  It's insane.

a = "abc\\"    # that's a string ending with one backslash
b = "def"
c = a + b

Looks OK to me.

> But Ruby has its own special brand of idiocy here.  Even Perl and PHP 
> get this right.

Perl is *exactly* the same.

#!/usr/bin/perl
print "abc\\\n";

This prints abc\ - same as Ruby would.

It was probably unfortunate that gsub uses sequences like \1 and the 
like in the substitution side though. But that's what perl does:

#!/usr/bin/perl
$_ = "ab&de\n";
s/&/\&/;
print;

That prints ab&de, which is the problem the OP was grappling with.
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