Two things worry me: In your version, (my-map list '(1 2 3) '(a b c)) results in an exception.
2: Replacing the internal calls to map by calls to my-map does not pass check-syntax. It may be my ignorance, though. I just started looking into TR. Jos > -----Original Message----- > From: Hari Prashanth [mailto:[email protected]] > Sent: 26 August 2010 20:17 > To: Jos Koot > Cc: PLT-Scheme Mailing List > Subject: Re: [racket] problem with map example in docs of typed/racket > > I think the example should be changed to > > (: my-map > (All (C A B ...) > ((A B ... B -> C) (Listof A) (Listof B) ... B -> > (Listof C)))) (define (my-map f as . bss) > (if (or (null? as) (ormap null? bss)) > null > (cons (apply f (car as) (map car bss)) > (apply my-map f (cdr as) (map cdr bss))))) > > > Hari > > ----- Original Message ----- > From: "Jos Koot" <[email protected]> > To: "PLT-Scheme Mailing List" <[email protected]> > Sent: Thursday, August 26, 2010 12:51:58 PM GMT -05:00 > US/Canada Eastern > Subject: [racket] problem with map example in docs of typed/racket > > > > See below, > Jos > > In definitions window > > #lang typed/racket > (: map > (All (C A B ...) > ((A B ... B -> C) (Listof A) (Listof B) ... B > -> > (Listof C)))) > (define (map f as . bss) > (if (or (null? as) > (ormap null? bss)) > null > (cons (apply f (car as) (map car bss)) ; These to lines > (apply map f (cdr as) (map cdr bss))))) ; are highlighted > > Run, then in interactions window: > > > Welcome to DrRacket, version > 5.0.1.3--2010-08-19(e55f0cade1d47b2edbc65e7dd61ddce2041814af/a) [3m]. > Language: typed/racket. > . Type Checker: Polymorphic function map could not be applied > to arguments: > Domain: (A B ... B -> C) (Listof A) (Listof B) ... B > Arguments: (All (a b) (case-lambda ((Pairof a b) -> a) > ((Listof a) -> a))) (List (Listof B) ... B) > in: (map car bss) > . Type Checker: Bad arguments to function in apply: > Domain: A B ... B > Arguments: A Nothing * > in: (apply f (car as) (map car bss)) > . Type Checker: Polymorphic function map could not be applied > to arguments: > Domain: (A B ... B -> C) (Listof A) (Listof B) ... B > Arguments: (All (a b) (case-lambda ((Pairof a b) -> b) > ((Listof a) -> (Listof a)))) (List (Listof B) ... B) > in: (map cdr bss) > . Type Checker: Bad arguments to polymorphic function in apply: > Domain: (A B ... B -> C) (Listof A) (Listof B) ... B > Arguments: (A B ... B -> C) (Listof A) Nothing * > in: (apply map f (cdr as) (map cdr bss)) . Type Checker: > Summary: 4 errors encountered in: > (map car bss) > (apply f (car as) (map car bss)) > (map cdr bss) > (apply map f (cdr as) (map cdr bss)) > > > > > > > > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/users _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
