From: Tom Cloyd <tomcloyd@...>
Date: 2008-06-16T15:21:24+09:00
Subject: array addressing problem

I know this is a simple problem - to 'most everyone but me, but I cannot 
see why I'm getting this error. I've explored things with ruby-debug, 
and with irb inside of the debugger, and I simply cannot replicate the 
error.

The code (this most of a little routine for converting an HTML file to a 
textile marked up file):

  # input
    filein = open( "{whatever}" )
    fi = filein.readlines
  # output
    fileout = open( "_textile.txt", 'w')
  delta = [
    ["</p>", ''],
    ["</h1>", '']] # for brevity, I've truncated this array - you get 
the idea, I assume
  ld = delta.length
  i = 0                 
  until i > ld
    #results = fi[0].gsub( delta[i][0], delta[i][1] )  <= in an attempt 
isolate error, I broke this into the following:
    s1 = delta[i][0]   # <= exception is thrown here
    s2 = delta[i][1]
    results = fi[0].gsub( s1, s2 )
    i += 1
    end

The error msg:

$ ruby textilemkr.rb
textilemkr.rb:55:in `main': undefined method `[]' for nil:NilClass 
(NoMethodError)
        from textilemkr.rb:66

I've confirmed that delta[1][0] is valid, that "i" is 0 when error 
occurs, etc.

If it works in irb, why doesn't it work when I run the routine via the 
interpreter? What obvious thing am I missing?

All help will be gratefully accepted.

Tom

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