From: "Peña, Botp" <botp@...>
Date: 2008-08-09T14:09:03+09:00
Subject: Re: Most compact command for associate array 'totalling'?

From: John Pritchard-williams [mailto:monojohnny@googlemail.com] 
# 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 ?

no. nil is a value and could be value for a hash key.

try
   
  h[mykey] = nil


the block form will invoke the block if the hash key does not exist

try

  h.has_key? mykey

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

imho, if you work on hashes, you should know block form of Hash.new. See ruby-doc for examples.

kind regards -botp