From: 7stud -- <bbxx789_05ss@...>
Date: 2009-09-12T06:25:25+09:00
Subject: Re: populating a hash from an array using inject

Glenn Jackman wrote:
> At 2009-09-11 02:07PM, "7stud --" wrote:
>>  
>>  bar = products.inject(Hash.new([])) {|h,p| [] << p; h}
>>  
>>  which does nothing to the hash--all it does is append p to an empty 
>>  array, and then the empty array is discarded.
> 
> As we've seen, it's not discarded:  it's kept for h's reference:
> 
>     products = [[1,2],[3,4],[1,5]]
>     foo = products.inject(Hash.new([])) {|h,(a,b)| h[a] << b; h} # => {}
>     foo[:unknown] # => [2, 4, 5]

...and this is  a lie too:

> If you access a non-existent key, say h["A"], then that line is 
> equivalent to

> baz = products.inject(Hash.new([])) {|h,p| h["A"] = [] + [p]; h}

You asked for lies.  I gave them to you.
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