Lazy evaluation alternative

[Chris Clearwater]

On Fri, Jan 24, 2003 at 01:51:57PM +0100, Jerzy Karczmarczuk wrote:
> Chris Clearwater wrote:
> >It seems to
> >me you could get some of the desired effects of lazy evaluation by using
> >continuation passing style in code. For example, take this psuedo-code
> >using CPS to represent an infinite data type.
> >
> >Using non-CPS this would be something like:
> >ones = 1 : ones
> >
> >using strict evaluation this would lead to an infinite loop.
> >
> >However using CPS this could be represented as:
> >ones c = c (1 : ones)
> >
> >where c is the continuation.
> >
> >This would not infinite loop as ones is still waiting for the
> >continuation argument. Another example:
> >
> >natural n c = c (n : natural n+1)
> 
> 
> Hey, Maestro, why don't you check before posting, hm? What is the type
> of ones? I am afraid you will get a nasty surprise...

Check what, the type? Or are you refering to the double posting? My
first message got rejected as I was not a member of the list so I
subscribed and reposted. It seems the moderator put it through anyways.

It seems the type would recursive? Is it that a problem?
Enlighten me? :)

> 
> ... BTW, are you sure there aren't any missing parentheses in the
> def. of natural? (But they won't help anyway...)

Yes I am. But the + should be in CPS form anyways to be perfectly
correct, so: natural n c = (+) n 1 (\m -> c n : (natural m))

> 
> 
> Jerzy Karczmarczuk
> 
> 
> 
>