In what situations should one prefer the `listof` combinator over an equivalent predicate contract?
For instance, it seems to me that: (λ(x) (and (list? x) (andmap pred? x))) is a more-or-less equivalent way of saying this: (listof pred?) But in my experience the predicate version is always significantly faster. Thus, is it generally better to rewrite contracts to avoid `listof`? And if so, when is `listof` still preferred? ;;;;;;;;;;;;;;;;;;;;;; ;; For instance. ;;;;;;;;;;;;;;;;;;;;;; #lang racket (define/contract (f1 xs) ((listof integer?) . -> . any/c) xs) (define (integers? x) (and (list? x) (andmap integer? x))) (define/contract (f2 xs) (integers? . -> . any/c) xs) (define (trial proc) (for ([i (in-range 1000)]) (proc (range 10000)))) (time (trial f1)) (time (trial f2)) ____________________ Racket Users list: http://lists.racket-lang.org/users
