In typed racket (- 1 1) and (- 2 2) are equal at runtime, but the type checker doesn't necessarily know that at compile time. It knows that (- 1 1) is zero because that's a special case in the type system. But it doesn't have a special case for (- 2 2), so it only knows that that's a Fixnum.
Alex Knauth > On Dec 10, 2015, at 12:26 PM, Klaus Ostermann <[email protected]> wrote: > > This Typed Racket term is well-typed: > > (+ 1 (if (= 0 (- 1 1)) 1 "x")) > > This one isn't: > > (+ 1 (if (= 0 (- 2 2)) 1 "x")) > > This looks a bit strange to me, because usually one would expect > well-typedness to be not destroyed by replacing "equals with equals". > > I'd like to know the rationale for this design. It would be nice if one of > the designers could comment on this. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
