gsub question

[Daniel Bretoi]

perl -e '$a="hello hi hello";$a =~ s/(\w+)/$1a/g;print $a; '
helloa hia helloa

ruby -e 'a="hello hi hello";a.gsub!(/(\w+)/,"#{$1}a"); puts a'
a a a

Why? I'm expecting the same result as in perl.

ruby -e 'a="hello hi hello";a.gsub!(/(\w+)/) { |k| k = k + "a"}; puts a'
helloa hia helloa

does however work.

Can someone try to explain why the first doesn't work?

db

 

[Jason Williams]

perl -e '$a="hello hi hello";$a =~ s/(\w+)/$1a/g;print $a; '
helloa hia helloa

ruby -e 'a="hello hi hello";a.gsub!(/(\w+)/,"#{$1}a"); puts a'
a a a

The interpolation (AIUI) is done before the string gets passed to
gsub!, so gsub! sees just the string "a". I think you want

a="hello hi hello";a.gsub!(/(\w+)/,'\1a'); puts a

 

[Jamis Buck]

perl -e '$a="hello hi hello";$a =~ s/(\w+)/$1a/g;print $a; '
helloa hia helloa

ruby -e 'a="hello hi hello";a.gsub!(/(\w+)/,"#{$1}a"); puts a'
a a a

Why? I'm expecting the same result as in perl.

Because the $1 isn't defined at the time the replacement string is
parsed. Instead, use \1:

ruby -e 'a="hello hi hello";a.gsub!(/(\w+)/, '\1a');puts a'
hello hia helloa