From: Robert Klemme <shortcutter@...>
Date: 2010-01-14T17:05:04+09:00
Subject: Re: Ruby Regex

2010/1/13 Marnen Laibow-Koser <marnen@marnen.org>:

> I'm glad to know that Ruby's backslash handling is not as weird as I'd
> thought.  Thanks for the correction.

:-)

For me there is actually something weird about Ruby's escape handling
- but it's something else: in some circumstances Ruby allows you to
*omit* a backslash which is meant to be convenient (I believe) but
which leads to a certain inconsistency:

irb(main):014:0> '\1'  # this might be seen as surprising
=> "\\1"
irb(main):015:0> '\\1'
=> "\\1"

We can get a single backslash by just using one, but if we need more
backslashes we need to escape:

irb(main):027:0> '\\1'
=> "\\1"
irb(main):028:0> '\\\1'
=> "\\\\1"
irb(main):029:0> '\\\\1'
=> "\\\\1"
irb(main):030:0> '\\\\\1'
=> "\\\\\\1"
irb(main):031:0> '\\\\\\1'
=> "\\\\\\1"

For double quoted strings we always need to use two backslashes at
least if followed by a digit:

irb(main):016:0> "\1"
=> "\x01"
irb(main):017:0> "\\1"
=> "\\1"

and

irb(main):018:0> '\n'  # this might be seen as surprising
=> "\\n"
irb(main):019:0> '\\n'
=> "\\n"

but

irb(main):020:0> "\n"  # a single newline
=> "\n"
irb(main):021:0> "\\n"  # backslash and n
=> "\\n"

Bottom line for me: I do not exploit the '\1' case and have made it a
habit to use two backslashes whenever I need a literal backslash in a
string.

Kind regards

robert


-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/