From: Brian Candler <b.candler@...>
Date: 2009-06-06T05:05:07+09:00
Subject: Re: Making nil comparable.

Robert Schaaf wrote:
> I have a array of foo objects, each of which contains an array bar
> values.  I'd like to sort the foos, ordered by the bars.  The problem
> is that the bars are of unequal length.
> 
> The most apt example is the numbering in an outline: 1, 1.1, 1.2,
> 1.2.1, 1.3 ...etc.
> 
> In practical terms, comparing 1.1 to 1.2.1 would be [1, 1, nil] <=>
> [1, 2, 1].  Array#sort_by barfs on the nil.  Is there some nice way to
> let nil always sort low?

irb(main):002:0> [1,1] <=> [1,2,1]
=> -1

So would

    sort_by { |x| x.bars.compact }

be sufficient?

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