From: Bob Showalter <bob_showalter@...>
Date: 2005-11-15T02:51:24+09:00
Subject: Re: [QUIZ][SOLUTION] Index and Query (#54)

Bob Showalter wrote:
>   # finds documents containing all of the specified terms.
>   # if a block is given, each document is supplied to the
>   # block, and nil is returned. Otherwise, an array of
>   # documents is returned.
>   def find(*terms)
>     @index.each do |document, mask|
>       if terms.all? { |term| @terms[term] && mask[@terms[term]] != 0 }
>         yield document
>       end
>     end
>   end

Oops, that comment is wrong. You must supply a block. I forgot to go 
back and add the support for returning an array.