CODEWITHSUNDEEP
rubyregex
sbagdat
sbagdat

Reputation: 850

Is this a Regexp bug or another thing?

I was playing with Ruby's Regexp. I supposed find a Regexp trick, but I can't understand, why?

  p a = "This is a test!".gsub!(//,'X')

Output of above is

  "XTXhXiXsX XiXsX XaX XtXeXsXtX!X"

It puts 'X' after and before any character in the test string. Anyone knows why?

Upvotes: 1

Views: 90

Answers (3)

SwiftMango
SwiftMango

Reputation: 15284

You asked it to match an empty space, so it matches every null space between letters.

It does not match a letter so all the letters remained.

Upvotes: 0

Jim Deville
Jim Deville

Reputation: 10662

You asked it to match a zero-width string (//), and replace it with 'X', so it did that. gsub scans the string and replaces every match (every letter boundary) with the replacement.

Upvotes: 2

sawa
sawa

Reputation: 168081

// matches substrings with zero width, i.e., empty strings. There are arbitrarily many empty strings in between any adjacent characters, but the gsub family does not keep matching at the same location. If it finds a match (i.e., the empty string in this case), then it will not match again at the same position, so it goes on to the empty string that is in between the next adjacent characters.

Upvotes: 3

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