> I've run into this multiple times as well, and would like someone (maybe me) > to write a package (maybe named `sugar-contract`) that provides this.
It would be neat, at least, to be able to use same double ellipsis notation as in defproc and as we read in the documentation: (-> hash? any/c any/c ... ... hash?) (Note: This would allow zero key/value pairs. But actually I think it's desirable for (safe-hash-aet h) simply to return h.) ---- p.s. I don't think it's _terrible_ to raise an error manually for something like this. You don't get the nice blame, is the drawback. For example: #lang racket/base (require racket/contract racket/match) ; (-> hash? any/c any/c ... ... hash?) (define (safe-hash-set h . _kvs) (let loop ([h h] [kvs _kvs]) (match kvs [(list) h] [(list* k v kvs) (loop (if (immutable? h) (hash-set h k v) (begin (hash-set! h k v) h)) kvs)] [(list v) (error 'safe-hash-set "expected sequence of key value ... ... but got:~n~v" _kvs)]))) (define imm-hash (hash 'a 1)) (define mut-hash (make-hash '((a . 1)))) (module+ test (require rackunit) (check-equal? (safe-hash-set imm-hash 'x 2) (hash 'a 1 'x 2)) (check-equal? (safe-hash-set imm-hash 'x 2 'y 7) (hash 'a 1 'x 2 'y 7)) (check-equal? (safe-hash-set mut-hash 'x 2) (make-hash '((a . 1) (x . 2)))) (check-equal? (safe-hash-set mut-hash 'x 2 'y 7) (make-hash '((y . 7) (a . 1) (x . 2)))) (check-exn exn:fail? (λ () (safe-hash-set (hash) 'x 2 'y)) "safe-hash-set: expected sequence of key value ... ... but got:\n'(x 2 y)")) -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.