Why does the first line return an empty string? Is this a bug or a
feature?
irb(main):001:0> a = “x”; a.gsub!(“x”,"\’")
=> “”
irb(main):002:0> a = “x”; a.gsub!(“x”,“y”)
=> “y”
On 2013-09-15, at 10:21 AM, “Sami S.” [email protected] wrote:
Why does the first line return an empty string? Is this a bug or a
feature?irb(main):001:0> a = “x”; a.gsub!(“x”,“\'”)
=> “”
irb(main):002:0> a = “x”; a.gsub!(“x”,“y”)
=> “y”–
Posted via http://www.ruby-forum.com/.
There are extra backslash sequences which work in substitution strings:
[1] pry(main)> a = “wxy”; puts a.gsub!(“x”,“\'”)
wyy
=> nil
Here ' is the “remains” of the string after the match, in the Pickaxe
book it tells about the additional backslash sequences in substitution
strings:
& last match
+ last matched group
` string prior to match
' string after match
\ literal backslash
So you need to escape the \ in ' to stop it being interpreted as the
string after match e.g.
[2] pry(main)> a = “wxy”; puts a.gsub!(“x”,“\\'”)
w'y
=> nil
Another approach might be to use a block where the returned string isn’t
using the additional backslash sequences:
[3] pry(main)> a = “wxy”; puts a.gsub!(“x”) { “\'” }
w'y
=> nil
Hope this helps,
Mike
–
Mike S. [email protected]
http://www.stok.ca/~mike/
The “`Stok’ disclaimers” apply.
Thank you for your answer. I’ve been reading the class reference at
(Class: String (Ruby 2.0.0)) which doesn’t mention the
backslash sequences…
regards,
Sami
Mike S. wrote in post #1121503:
On 2013-09-15, at 10:21 AM, “Sami S.” [email protected] wrote:
Here ' is the “remains” of the string after the match, in the Pickaxe
book it tells about the additional backslash sequences in substitution
strings:& last match
+ last matched group
` string prior to match
' string after match
\ literal backslash