From: Joel VanderWerf <vjoel@...>
Date: 2006-01-31T15:13:53+09:00
Subject: Re: Array prepending nil object

Serdar K脹l脹巽 wrote:
> I'm going through Brian Schr旦der's tutorial and hit a small snag. The
> code is (on page 16):
> 
> print 'Array as stack: '
> stack = Array.new()
> stack.push('a')
> stack.push('b')
> stack.push('c')
> print stack.pop until stack.empty?
> 
> The display that I'm getting is:
> Array as stack: cbanil
> 
> So somehow nil is creeping it's way into my array but I'm not sure
> how. Any ideas?

The nil is just the return value of the last expression, not part of the
output of the print calls.

You can see it more clearly in irb:

irb(main):001:0> print 'Array as stack: '
Array as stack: => nil
irb(main):002:0> stack = Array.new()
=> []
irb(main):003:0> stack.push('a')
=> ["a"]
irb(main):004:0> stack.push('b')
=> ["a", "b"]
irb(main):005:0> stack.push('c')
=> ["a", "b", "c"]
irb(main):006:0> print stack.pop until stack.empty?
cba=> nil

The printed output shows up on the left of the =>.

-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407