From: Florian Frank <flori@...>
Date: 2005-10-20T05:34:49+09:00
Subject: Re: Functional with Ruby

Louis J Scoras wrote:

>Yes, it is ultimately defined recursively, but the complexity is pushed down
>into the fold* functions. Granted it's a pretty simple recursion, but the
>point still holds.
>  
>
I think the point is, that you can use foldr, a function that is defined 
in Haskell only in terms of recursion. But Ruby's inject isn't defined 
in Ruby, it's a method of Array (a stateful data structure) written in C 
and it is actually implemented iterative. The Ruby version isn't really 
functional, it's only very similar, while the Haskell foldr is a 
recursivley defined function. So if you want to play with functional 
style programming in Ruby, using Array#inject is a bit fishy.

On the other hand, if you want to write a reasonable fast program in 
Ruby, I would avoid recursion as much as possible, go for iteration, and 
concentrate on using methods implemented in C instead. But it seemed to 
me, that the OP was more interested  in learning about functional 
programming (using Ruby as well as Haskell), than writing fast programs.

-- 
Florian Frank