[r6rs-discuss] Compile-time detection of contract violations

From: Robby Findler <robby>
Date: Sun Oct 29 20:37:11 2006

At Thu, 26 Oct 2006 10:23:42 -0400, William D Clinger wrote:
> Jason Orendorff wrote:
> > What about at compile time? Does R5.91RS allow an implementation to
> > detect a contract violation at compile time and reject the program? I
> > couldn't find any such wording. I think this should be allowed.
>
> It is, I think. Section 9.22 of the R5.91RS draft says:
>
> Most implementations are able to recognize some violations
> when parsing, expanding macros, or compiling a definition
> or expression whose evaluation has not yet commenced in
> the usual sense. Implementations are allowed to use
> nonstandard exception handlers at those times, and are
> encouraged to raise &syntax exceptions for violations
> detected at those times, even if the definition or
> expression that contains the violation will never be
> executed. Implementations are also allowed to raise
> a &warning exception at those times if they determine
> that some subexpression would inevitably raise some
> kind of &violation exception were it ever to be
> evaluated.


Does this mean that, in conforming implementations of r6, this
expression:

 (with-exception-handler (lambda (x) 1) (lambda () (cons 1 2 3)))

might produce 1 and might signal an error (at compile time)?

Robby
Received on Thu Oct 26 2006 - 13:07:39 UTC