Ian Lynagh wrote: > http://hackage.haskell.org/trac/haskell-prime/wiki/Defaulting#Proposal4- removedefaulting >
Here's a late response to the comments on that wiki page. It seems, to me, an extremely bad idea to remove defaulting *and* make that proposed change to (^) at the same time. Code can currently depend on defaulting, and if it does, then integers most likely default to the Integer type, not Int. If you just remove defaulting, then that code fails to compile, which is fine. If you remove defaulting and change (^) at the same time, then that code compiles but means something different, which is definitely not fine. It may initially seem like there's no problem, since no one would possibly want to use a number anywhere near 2 billion as an exponent for (^). The problem here is that if one is allowing types to be inferred (which is certainly true, if we're worried about defaulting), then that use of the horribly unsafe Int type can propogate through the code. Do I use this number as an exponent, and then also add it to x somewhere else? Then x is an Int as well. Then maybe I calculate (x * y) somewhere else? Okay, now y is an Int. And perhaps y is added to z? So, z is an Int. But maybe z overflows... and now a nasty bug, a numeric overflow in z, was introduced without changing my code, without a warning, by the change to the type of (^) which is used four functions away. -- Chris _______________________________________________ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
