[mercury-users] What does logic buy us over pure functional programming?

[Roy Ward]

on 30/4/01 11:40 PM, Terrence Brannon at princepawn at earthlink.net wrote:

> 1 - reversable functions. In other words, it seems to be a wonderful
> thing to have a version of append that appends input to output, but
> also one which shows what input might have made the output. However,
> this is do-able in functional languages too.

Alongside this, predicates that can have multiple 'return'
values.

such as:
:- pred f(int::in, int::in, int::out, int::out) is det.

Most of the functional languages I have used only allow one
return value (There are exceptions to this, and my experience
with functional languages is not vast). Yes I know that you
can return structures encapsulating multiple return values,
but I really appreciate being able to do the above without
messing around.

I largely use Mercury as what I'd consider a functional
language (nearly all my code is det or semidet), but that
might be just my functional bias.

Cheers,
Roy Ward.



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