[racket-dev] contract-out

20 minutes ago, Sam Tobin-Hochstadt wrote:
> On Sun, Sep 25, 2011 at 9:36 PM, Eli Barzilay <eli at barzilay.org> wrote:
> > An hour and a half ago, Sam Tobin-Hochstadt wrote:
> >> On Sun, Sep 25, 2011 at 8:14 PM, Eli Barzilay <eli at barzilay.org> wrote:
> >> > IMO, a better approach for disabling contracts is to have the
> >> > client decide whether it wants the contracted version or the plain
> >> > one -- which is a rough mirror of how unsafe operations are done
> >> > (with the choice being made by requiring one file or
> >> > another).  Then, there could be a facility that associates a safe
> >> > identifier with an unsafe version, so you could write (unsafe foo)
> >> > -- which will be the unsafe operation for builtins that have one,
> >> > and in case of a contracted function it will be the uncontracted
> >> > one.
> >>
> >> This wouldn't work for the Typed Racket use case, where I want to flip
> >> one switch for contracts throughout the TR code base.
> >
> > (define-for-syntax contracts-on? #t)
> >
> > (define-syntax (switch stx)
> >  (syntax-case stx ()
> >    [(_ id) (if contracts-on? #'id #'(unsafe id))]))
> 
> But now I have to change all the places that use these identifiers.

Yes, you make it all go through that macro, and the problem is solved.


> The "turn on and off internal contracts" and "give me unchecked
> access to this library" use cases are genuinely different.

Such a macro makes it possible to easily turn off all contracts.
Meanwhile, you get to keep the contract information and use it for
other purposes where it's still useful.

-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                    http://barzilay.org/                   Maze is Life!