If you update $~ (the match result), $&, $1, etc. would follow
accordingly. So that the better RCR should be to create MatchData
without built-in regular expression match, I think.
Wow, this solves a problem I was dealing with. I wanted to implement “sub”
on a array-like object such that list.sub(…) would be the same a calling
sub on each element of the list. The problem was that list.sub(/re/) { $1 }
would always give nil for the value of $1.
Here’s my solution.
-----------------------------------------------
class FileList < Array
class << self
attr_accessor :match_data
def set_match_data(md, block)
FileList.match_data = md
eval “$~ = FileList.match_data”, block
end
end
def sub(re, &block)
collect do |item|
item.sub(re) {
FileList.set_match_data($~, block)
block.call
}
end
end
end
f = FileList.new
f << “a.c” << “b.c”
p f.sub(/^(.*).c$/) { “#{$1}.o” }
---------------------------------------------
The above solution is not thread safe, but that can be easily solved by
using a mutex in set_match_data. Comments welcome.
···
From: matz@ruby-lang.org [mailto:matz@ruby-lang.org]
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