From: Mikael Brockman <phubuh@...>
Date: 2004-07-10T05:25:47+09:00
Subject: Re: Functional Ruby (Re: Why I don't use Ruby.)

"Sean O'Dell" <sean@celsoft.com> writes:

> On Friday 09 July 2004 05:02, Florian Gross wrote:
>> Sean O'Dell wrote:
>> >
>> > You can have variables in a functional language, but what you can't have
>> > are globals that act statefully, causing any functions you write to
>> > return different values when passed the same parameter values.  You can
>> > have (pseudocoded):
>>
>> As far as I know LISP does indeed have closures -- and I can emulate
>> globals with them in Ruby like this:
>>
>> Oh, and about not having side-effects: Most functional languages have
>> them when doing I/O.
>
> I don't remember closures from my LISP days, but perhaps that's a memory 
> issue.

Ancient Lisps, such as Emacs Lisp, lack closures.  They have anonymous
functions, but they're dynamically scoped.  Dynamical scoping is
occasionally useful, but it mostly sucks.  Non-ancient Lisps, starting
with Scheme, use lexical scoping.

> I/O has always been an exception, but I think you have to have 
> exceptions to get variance into the program and I/O is a common programming 
> paradigm and a great way to introduce variance.

Note that there are purely functional languages with I/O: Haskell,
Clean, Miranda, and probably more.

  mikael