From: John Pritchard-williams <monojohnny@...>
Date: 2008-08-09T00:47:13+09:00
Subject: Re: Most compact command for associate array 'totalling'?

Thanks for the replies: in fact I also prefer this one:

//
a = Hash.new(0)
a['abc'] += 1
//

As it matches exactly the behaviour of the 'awk' program and its also 
kinda neat looking.

On the other hand this solution is also really intriguing:  ( and I note 
the difference in behaviour as explained earlier in this post):

//
h=Hash.new{|h,k| h[k]=0}
//

So can somebody explain in English what is going on here ? This is very 
very Ruby to me :-) I'm guessing that we are hanging that block of the 
'store' method of 'h' from now on ? I mean: so when somebody then calls 
something like:

h.store(mykey,myvalue) it will invoke the block which will result in:

h[mykey]=myvalue - but only if 'myvalue' is nil ?

Is this a very specific mechanism to hashes or something really generic?

Thanks again !

John
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