[plt-scheme] Recursive types and their specification

--- Robby Findler <robby at cs.uchicago.edu> wrote:

> Did you try using a datatype to do that?

Nope.  Being a faithful student of HtDP I decorate my
Scheme programs with type declarations in the comments, so
this question arose from Scheme programming, not <your
favourite statically typed FPL>.  I couldn't see a way to
write down the type without going introducing extra
machinery

--- Matthew Flatt <mflatt at cs.utah.edu> wrote:

> Yes. As your subject line says, the problem is a
> equi-recursive function type
> 
>   mu x . () -> (action * x)
> 
> which is not in the type system.
> 

Thanks.  This is interesting.  Had I the time, I'd read
more about this (Google turns up some interesting hits); as
it is, back to Pacman.

Cheers,
Noel

Email: noelwelsh <at> yahoo <dot> com   noel <at> untyped <dot> com
AIM: noelhwelsh
Blogs: http://monospaced.blogspot.com/  http://www.untyped.com/untyping/

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