Using array results from ruby gsub method and a match block

Question

I'm working through the Ruby koans and have hit one that's really confusing me.

"one two-three".gsub(/(t\w*)/) { $1[0, 1] }
 => "one t-t"

However, when I modify the return array for the $1 variable, I get a confusing result.

"one two-three".gsub(/(t\w*)/) { $1[1, 2] }
 => "one wo-hr"

Given the first result, I'd expect the second bit of code to return "one wh". Why are two characters being returned in the second instance?

Answer 1

You expect "one wh" which would be the result of this:

"one two-three".gsub(/(t\w*)/) { $1[1, 1] }

[] is a method on string where a range can be provided like so:

str[start, length]

so the 2 in your code is actually the length (ie number of characters)