On Mon, Jun 24, 2013 at 8:21 AM, Matthias Felleisen <matth...@ccs.neu.edu> wrote: > > On Jun 23, 2013, at 8:34 PM, Sam Tobin-Hochstadt wrote: > >>> >>> After porting nearly everything I was left with typing up the command-line >>> parser. However, I am getting a type error at the following simplified part: >> >> Here's a version that type checks: https://gist.github.com/samth/5847063 >> >> The key is giving a type annotation to `fname` using the #{} syntax. >> Typed Racket can figure out how to typecheck the expansion only if you >> give it that hint. And the #{} syntax is for adding such hints with >> macros like `command-line` that didn't anticipate Typed Racket. > > > I think this answer is not fair. > > Because > > On Jun 23, 2013, at 2:21 PM, Tim K. wrote: > >> I wonder, why does fname have the "Any" type? Yes, I didn't explicitly give >> fname a type, but I was hoping that the typed version of "command-line" >> would do that > > is correct. command-line in a typed context should know that what flows into > its world is a string.
This could mean one of two things. One is that `command-line` could be treated specially in Typed Racket (or there's a `typed/racket/command-line` library), so that it's like those identifiers were already given the type `String`. This would be technically challenging (without requiring the extra library), and is, I think, a bad idea. The other is that Typed Racket could improve its inference, so that it can just tell that only `String` is possible there. This is my preferred solution, but it will require some significant work on improving inference in Typed Racket that I don't think will happen in the very near future. Sam ____________________ Racket Users list: http://lists.racket-lang.org/users
