From: Brian Candler <b.candler@...>
Date: 2010-01-08T18:57:56+09:00
Subject: Re: Stopping String Escaping.

Phil Cooper-king wrote:
> un_parsed =<<ENDOF
>   \\
> ENDOF

Unfortunately, here the \\ is being turned into a single backslash by 
ruby, the same as inside a quoted string. In other words, the same as 
this:

irb(main):001:0> "\\".size
=> 1
irb(main):002:0> '\\'.size
=> 1

The simplest way of preventing this is to read unparsed from a file, or 
you can have an inline dataset at the end of your source code, like 
this:

unparsed = DATA.read
... rest of your code goes here

__END__
\\

> I expect the \ to be lost in puts 
> tho.

No, puts *never* converts two backslashes into one. If your string 
contains two backslashes, puts will show two backslashes.

> Using the dump I see the double slash is still there.

No, this is the opposite. String#inspect turns a raw string into a 
quoted string for display purposes, and as part of this quoting a single 
backslash is displayed as two backslashes.

Look at this:

irb(main):001:0> s = 92.chr
=> "\\"
irb(main):002:0> s.size
=> 1
irb(main):003:0> puts s
\
=> nil
irb(main):004:0> s2 = s + s
=> "\\\\"
irb(main):005:0> s2.size
=> 2
irb(main):006:0> puts s2
\\
=> nil

Hopefully it's clear from the above that string s has one character (a 
single backslash), and s2 has two backslashes. But these are displayed 
in quoted form in irb as

"\\"
"\\\\"

respectively. puts displays them correctly.

Similarly, a single newline character is displayed as backslash-n when 
inspect gives the quoted form; whereas puts actually prints a newline.

irb(main):009:0> nl = 10.chr
=> "\n"
irb(main):010:0> nl.size
=> 1
irb(main):011:0> puts nl

=> nil

So try your test case again:
(1) Use the DATA.read / __END__ to get the test source in
(2) Use 'puts' and not 'dump' to see clearly what you have
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