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Re: Common Lisp solved this problem 20 years ago

This page is part of the web mail archives of SRFI 77 from before July 7th, 2015. The new archives for SRFI 77 contain all messages, not just those from before July 7th, 2015.

Alan Watson wrote:
I have realized (remembered?) that type specifiers are only one of the ingredients in this particular recipe for solving this problem.

For example, consider the following in Kawa's notation:

  (lambda (x :: <flonum> y :: <flonum>) :: <flonum>
    (/ x y))

Unless the compiler can be sure that / is the standard division procedure, there is not much it can do.

Of course, module systems often allow the compiler to figure out what / really is, and a module system will come fitted as standard in R6RS.

Common Lisp allows a compiler to *assume* / is defined to the standard
/ operation, unless there is a visible re-definition.
Kawa makes more-or-less the same assumpions.
I think that is a reasonable default mode for a compiler.

Also note I am assuming "compatible run-time typing" and behavior:
	--Per Bothner
per@xxxxxxxxxxx   http://per.bothner.com/