From: Michael Neumann <neumann@...>
Date: 2001-06-04T07:47:35+09:00
Subject: [ruby-talk:16191] Re: RCR: treatment of ranges within array definitions

Phil Tomson wrote:
> 
> 
> [I sent this yesterday via the newsgroup comp.lang.ruby, but I don't think
> it ever went anywhere, so now I'm sending to the mailing list - sorry if
> it's a duplication]
> 
> I've been converting a lot of perl code to Ruby lately.
> 
> In perl if I put a range into an array that range is expanded so that the
> array contains each element described by the range (Perl doesn't have a
> range type).  So in perl if I do:
> 
> (0..4,8,10..12)
> I get an array that contains:
> (0,1,2,3,4,8,10,11,12)
> 
> If I declare an array in Ruby this way:
> array = [0..4,8,10..12]
> array contains three elements, the first and third elements are of range
> type.

This currently works in Ruby:

  array = [*1..3]           # => [1, 2, 3]
  array = [*(1..3)]         # => [1, 2, 3]

  array = [0, *(1..3)]      # TypeError, failed to convert Range into Array ????
  array = [0, *(1..3).to_a] # => [0,1,2,3] 

  But after the * may not be any further parameter, so the following gives a parse error:

  array = [*(0..2).to_a, 3]

  I don't know why the TypeError is raised? Can someone tell me?
  The '*' normally calls #to_a, isn't it, and #to_a is defined by class Range.

  If we would allow '*' to be everywhere inside a parameter list, this would 
  solve your problem, so you could write [*0..4,8,*10..12]. But I don't know 
  if this would be possible, because the parser had to be changed.
  
Regards,

  Michael

-- 
Michael Neumann
merlin.zwo InfoDesign GmbH
http://www.merlin-zwo.de