2Robby: > (define/contract (test f) (-> (->* (input-port? any/c) #:rest list? any) any) 1) > (test (λ (x y) 2)) . . test: contract violation expected: a procedure that accepts 2 non-keyword arguments and arbitrarily many more given: #<procedure> accepts: 2 arguments in: the 1st argument of (-> (->* (input-port? any/c) #:rest list? any) any) contract from: (function test) blaming: anonymous-module at: unsaved-editor322:14.20
So doesn't work. 2Alexander: procedure-has-arity is not needed. I can write: > (define/contract (test f) (-> (or/c (-> input-port? any/c any) (-> input-port? any/c any/c any) (-> input-port? any/c any/c any/c any) (->* (input-port? any/c) #:rest list? any)) any) 1) > (test (λ (x y) 2)) 1 But I need any number of args, more than two. I can, of course write something like (define-syntax (make-contract stx) (syntax-case stx () [_ (with-syntax ([(CLAUSES ...) (for/list ([i 100]) ;;; hope 100 enough many #`(-> input-port? any/c #,@(for/list ([j i]) #'any/c)))]) #'(or/c CLAUSES ... (->* (input-port? any/c) #:rest list? any)))])) But it is very slow and clumsy. Sun, 29 Jun 2014 18:43:15 -0500 от Robby Findler <[email protected]>: >Why isn't: > > (->* (input-port? any/c) #:rest list? any) > >by itself the contract that you want? > >Robby > > >On Sun, Jun 29, 2014 at 12:08 PM, Alexander D. Knauth >< [email protected] > wrote: >> You can use or/c to do this, as long as you guard them like this so that no >> more than one contract matches at a time: >> (or/c >> (and/c (procedure-has-arity/c 2) (-> input-port? any/c any)) >> (and/c (procedure-has-arity/c 3) (-> input-port? any/c any/c any)) >> (and/c (procedure-has-arity/c 4) (-> input-port? any/c any/c any/c any)) >> (->* (input-port? any/c) #:rest list? any) >> ) >> >> Or, you could use if/c from unstable/contract, or define a cond/c macro like >> this: >> (require unstable/contract) >> (define-syntax cond/c >> (syntax-rules (else) >> [(cond/c) none/c] >> [(cond/c [else else-c]) >> else-c] >> [(cond/c [pred then-c] clause ...) >> (if/c pred >> then-c >> (cond/c clause ...))])) >> >> (cond/c [(procedure-has-arity/c 2) (-> input-port? any/c any)] >> [(procedure-has-arity/c 3) (-> input-port? any/c any/c any)] >> [(procedure-has-arity/c 4) (-> input-port? any/c any/c any/c any)] >> [else (->* (input-port? any/c) #:rest list? any)]) >> >> By the way it has to be procedure-has-arity/c, not >> procedure-includes-arity/c: >> (define (procedure-has-arity/c arity) >> (define normalized-arity (normalize-arity arity)) >> (flat-named-contract >> `(procedure-has-arity/c ,normalized-arity) >> (λ (f) >> (and (procedure? f) >> (arity=? (procedure-arity f) normalized-arity))))) >> >> On Jun 29, 2014, at 8:00 AM, Roman Klochkov < [email protected] > wrote: >> >> How to make a contract, that accepts >> (-> input-port? any/c any) >> (-> input-port? any/c any/c any) >> (-> input-port? any/c any/c any/c any) >> ... >> and >> (->* (input-port? any/c) #:rest list? any) >> >> >> So theare should be at least two args and first arg should be input-port. >> >> -- >> Roman Klochkov >> >> ____________________ >> Racket Users list: >> http://lists.racket-lang.org/users >> >> >> >> ____________________ >> Racket Users list: >> http://lists.racket-lang.org/users >> -- Roman Klochkov
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