From: Kent Dahl <kentda@...>
Date: 2002-11-12T05:47:09+09:00
Subject: Re: What the...?

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.

-- 
(\[ Kent Dahl ]/)_    _~_    __[ http://www.stud.ntnu.no/~kentda/ ]___/~
 ))\_student_/((  \__d L b__/  NTNU - graduate engineering - 5. year  )
( \__\_�|�_/__/ ) _)Industrial economics and technological management(
 \____/_�_\____/ (____engineering.discipline_=_Computer::Technology___)