personal note 5 : Reading RegEx

(1) What happened
I had trouble at RegEx while editing my CC_FG.

In line 300 in Window_Base;
  #--------------------------------------------------------------------------
  # * Destructively Get Control Code Argument
  #--------------------------------------------------------------------------
   def obtain_escape_param(text)
    text.slice!(/^\[\d+\]/)[/\d+/].to_i rescue 0
  end
What is that [/\d+/] ?
That single line crashed my whole night.

Perhaps I'll forget what does this line say, so leaving this note.

(2) Decryption
That bracketed RegEx ([/\d+/]) is one style of [] for String.
It returns a matched part of String.

Example:
"hoge01"[0] => "h"
"hoge01"[/\d+/] => "01"

so a collapsed form of the line means;

begin
  str = text.slice!(/^\[\d+\]/)
  str.match(/\d+/)
  str = $&.to_i
rescue
  0
end

(3) Application

And from there, I made a line to get String parameter.
  str = text.slice!(/^\[.+?\]/)
  str.match(/\[(.+?)\]/)
  str = $1
or
  str.match(/\[(.+?)\]/)[1]
or
  text.slice!(/^\[\S+\]/)[/\[(.+?)\]/, 1]
I will not use the compressed RegEx line though.

(4) Biproduct

Class Window_Base < Window
  def obtain_escape_param_string(text)
    text.slice!(/^\[\S+\]/)[/\[(.+?)\]/, 1] rescue 0
  end
end

This allows us to take a parameter as String for control characters in RMVXA.
I thought I need this method in CC_FG at first, but not in result.

('w')