Puts "\\".gsub("\\", "\\\\")

ruby-talk
1

Hello, I have a mini-ruby quiz. Guess what this line of code writes to
the console, then try it for yourself:

puts "\\".gsub("\\", "\\\\")

Why is that so?

Martin

2

# Hello, I have a mini-ruby quiz. Guess what this line of code writes to
# the console, then try it for yourself:
# puts "\\".gsub("\\", "\\\\")

puts "\\".gsub("\\", "\\\\")
\
#=> nil

# Why is that so?

faq. escaping the escape in sub/gsub. search the archives.

maybe you want something like,

puts "\\".gsub("\\"){"\\\\"}
\\
#=> nil

ie, use block wc is a lot more handy.

kind regards -botp

···

From: martinus [mailto:martin.ankerl@gmail.com]

3

* martinus <martin.ankerl@gmail.com> (11:53) schrieb:

Hello, I have a mini-ruby quiz. Guess what this line of code writes to
the console, then try it for yourself:

puts "\\".gsub("\\", "\\\\")

Why is that so?

Well, it's an faq. In short: The backslash is special in strings *and*
in the replacement text. So for every literal backslash you need four
backslashes, which is quite unreadable. If you don't need \1 and Co you
better use the block form: gsub("\\") { "\\\\" }.

mfg, simon .... hth

4

We were just up and down this road (and I gave a workaround):

<http://groups.google.com/group/comp.lang.ruby/msg/d370b684485c8838&gt;

m.

···

martinus <martin.ankerl@gmail.com> wrote:

Hello, I have a mini-ruby quiz. Guess what this line of code writes to
the console, then try it for yourself:

puts "\\".gsub("\\", "\\\\")

--
matt neuburg, phd = matt@tidbits.com, Matt Neuburg’s Home Page
Leopard - http://www.takecontrolbooks.com/leopard-customizing.html
AppleScript - http://www.amazon.com/gp/product/0596102119
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5

Another thing which trips up newbies, and sometimes not so newbies, is
the difference between the contents of a sring, and the 'inspect'
presentation of a string, particularly when the string contains
escapes:

irb(main):001:0> puts "\\"
\
=> nil
irb(main):002:0> p "\\"
"\\"
=> nil

The point is that the literal string "\\" only contains one character.
The puts method shows you the contents of the string, while p (which
is practically equivalent to puts string.inspect produces a literal
representation.

···

On Thu, Apr 24, 2008 at 8:35 AM, Simon Krahnke <overlord@gmx.li> wrote:

* martinus <martin.ankerl@gmail.com> (11:53) schrieb:

> Hello, I have a mini-ruby quiz. Guess what this line of code writes to
> the console, then try it for yourself:
>
> puts "\\".gsub("\\", "\\\\")
>
> Why is that so?

Well, it's an faq. In short: The backslash is special in strings *and*
in the replacement text. So for every literal backslash you need four
backslashes, which is quite unreadable. If you don't need \1 and Co you
better use the block form: gsub("\\") { "\\\\" }.

--
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/