From: Louis J Scoras <louis.j.scoras@...>
Date: 2005-10-20T04:56:54+09:00
Subject: Re: Functional with Ruby

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Yes, it is ultimately defined recursively, but the complexity is pushed dow=
n
into the fold* functions. Granted it's a pretty simple recursion, but the
point still holds.

You can create iterators (isomorphisms, whatever you want to call them) ove=
r
any arbitrary data structure, then use higher order functions to get the
behaviour you want. A more helpful one might be over a binary search tree,
create a function which iterates over the nodes, in say infix order. Then
you never have to write such boring code ever again.

Which is why this:

a.inject(0){|sum,i| sum+i}


Is preferable to this:

def listsum(x)
> x.size =3D=3D 0 ? 0 : x[0] + listsum(x[1..-1])
> end


The point is that this can be used to define any number of functions over a
list, and it's more readable. I'm pulling these out of thin air. Supposed t=
o
be length and concat...

foldr (+ 1) 0 list
foldr (.) "" list

et cetra.

[ I'm sure there's probably more errors in those by the way. I really need
to try writing some Haskell again. I'm sick enough to have actually enjoyed
implementing state monads =3D) ]

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