Well, you can't do it like that, but you can like this:
#lang typed/racket
(: test0 (Integer [#:zero Integer] -> Boolean))
(define (test0 x #:zero [v 0])
(= x v))
I think the `Keyword' type is for symbols that happen to be keywords:
(cast '#:zero Keyword)
I believe there is currently no way to type a function that has required
keywords; i.e. they have to be optional.
Neil ⊥
On 02/20/2013 03:48 PM, Norman Gray wrote:
Greetings.
Should I be able to specify a function which can take keywords, in Typed Racket?
The 'define:' form suggests not, and an experiment with:
(define test0
(case-lambda:
(((x : Integer))
(= x 0))
(((x : Integer)
(k : Keyword)
(v : Integer))
(begin
(eprintf "x=~s k=~s v=~s~%" x k v)
(= x v)))))
similarly suggests not. I get
(test0 1 #:keyword 1)
Type Checker: No function domains matched in function application:
Domains: Integer
Integer Keyword Integer
Arguments: One
in: (test0 1 #:keyword 1)
I'm guessing that the recommended alternative would be
(define test0
(case-lambda:
(((x : Integer))
(= x 0))
(((x : Integer)
(k : (U 'k1 'k2))
(v : Integer))
(begin
(eprintf "x=~s k=~s v=~s~%" x k v)
(= x v)))))
Would that be right?
And what would be good style here? (I can broadly see why keywords might be
difficult or low-priority in this context, so I suppose that the style question
is the main thing here)
I can't see any use of 'Keyword' in the tree under collects/typed.
Thanks for any illumination.
All the best,
Norman
(having another go with Typed Racket)
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