From: Austin Ziegler <austin@...>
Date: 2002-11-12T05:55:50+09:00
Subject: Re: What the...?

On Tue, 12 Nov 2002 05:47:09 +0900, Kent Dahl wrote:
> Johan Persson wrote:
>> Take a look on the snippet below
>> # points is an array of structure-objects defining a point
>> points[0].x = 5
>> points[0].y = 4
>> 1.upto(points.length) { |i|
>>  points[i].x = points[i-1].x
>>  points[i].y = points[i-1].y
>> }
>> 
>> Now that looks like a legal bunch of statements, right? The thing
>> is every time Ruby interpret the line 'points[i].x =
>> points[i-1].x' it stops, giving me nothing but a cryptic error
>> message, 'undefined method `x=' for nil (NameError)'. Could
>> someone please tell me what's going on?
> Array indexing starts at 0.
> 1.upto iterates _including_ points.length, which doesn't exist,
> meaning [] returns nil... and you can guess the rest.
> 
> Try
> 0.upto(points.length-1) { |i|
> instead.

Actually, becuase he's manually handling index 0, he would want:

  1.upto(points.length - 1) { |i| ... }

-austin
-- Austin Ziegler, austin@halostatue.ca on 2002.11.11 at 15.54.29