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Re: meta-comment on typing



John.Cowan wrote:
Per Bothner scripsit:


It's a choice bwteeen:
(define (square-sum (x :: <flonum>) (y :: <flonum>))
 (+ (* x x) (* y y)))
or:
(define (square-sum x y)
 (fl+ (fl* x x) (fl* y)))
If you have type specifiers, you don't need the separate operation
names.  And type specifiers are much to be preferred.  After all
if Scheme is a teaching language, we want to encourage our students
to use type declarations, I think.


Unless you want to add overloading to Scheme, you have just pushed off the
problem from the predefined names to the user-defined names, as the above
will need to be complemented by a version of square-sum that does fixnums.

Huh?  You're comparing apples and oranges.  The srfi-77 version:
(define (square-sum x y)
  (fl+ (fl* x x) (fl* y)))
doesn't do fixnums either.  Perhaps I misunderstand your point.

Yes, another advantage of type declarations is that one *can* (somewhat
more readily) add overloading (as Kawa and some other Scheme dialects
do).  But that's not what I'm arguing for.

My argument is that:
* Adding optional type declarations to Scheme is desirable for a number
of reasons, not just performance - or overloading.
* Once one has optional type declarations, the need for type-specific
arithmetic primitives is reduced or eliminated.
* As a matter of style, I believe type declarations are preferable to
type-specific arithmetic primitives, especially since Type Declarations
are Good in themselves.
--
	--Per Bothner
per@xxxxxxxxxxx   http://per.bothner.com/