3 Contracts
| (require scramble/contract) | package: scramble-lib |
Added in version 0.4 of package scramble-lib.
procedure
(vectorof/ic elem/c) → impersonator-contract?
elem/c : contract?
procedure
(hash/ic key/c value/c) → impersonator-contract?
key/c : contract? value/c : contract?
value
value
> (define the-vector (vector))
> (define/contract install! (-> (vectorof/ic real?) void?) (lambda (v) (set! the-vector v))) > (define v (vector 1 2 3)) > (install! v) > (vector-set! v 0 'apple) > (vector-set! v 1 'banana) > (eq? the-vector v) #f
> (vector-ref the-vector 0) 1
If the original value is suitable, the contract projection returns it unchanged.
> (define imm-vec '#(1 2 3)) > (install! imm-vec) > (eq? the-vector imm-vec) #t
The value produced by a hash/ic contract uses the same key comparison as the original value.
> (define/contract hash-snapshot (-> (hash/ic any/c any/c) any) (lambda (h) h)) > (hash-snapshot (make-hasheqv '((1 . "one") (2 . two)))) '#hasheqv((1 . "one") (2 . two))
> (hash-snapshot (hash '(1 2 3) 6 '(4 5) 9)) '#hash(((4 5) . 9) ((1 2 3) . 6))
procedure
(hash-record/ic key=>value/c [ #:name name #:other get-other/c #:required required]) → impersonator-contract? key=>value/c : (hash/c any/c contract?) name : any/c = '(hash-record/ic ....) get-other/c : (-> any/c contract?) = (lambda (key) any/c) required : (or/c 'all list?) = 'all
If required is 'all, then every key of key=>value/c is required. If required is a list, each element must be a key of key=>value/c, and only those keys are considered required.
> (define point/c (hash-record/ic (hash 'x real? 'y real?)))
> (define/contract point-taxi-dist (-> point/c real?) (lambda (p) (+ (abs (hash-ref p 'x)) (abs (hash-ref p 'y))))) > (point-taxi-dist (hash 'x 5 'y 3)) 8
> (point-taxi-dist (hash 'x 5 'y 3 'elevation -10)) 8
> (point-taxi-dist (hash 'x 5 'y 'north)) point-taxi-dist: contract violation
expected: real?
given: 'north
in: the 'y field of
the 1st argument of
(-> (hash-record/ic ....) real?)
contract from: (definition point-taxi-dist)
blaming: top-level
(assuming the contract is correct)
at: eval:17:0
> (point-taxi-dist (hash 'x 5)) point-taxi-dist: contract violation
expected: hash with 'y key
given: '#hash((x . 5))
in: the 1st argument of
(-> (hash-record/ic ....) real?)
contract from: (definition point-taxi-dist)
blaming: top-level
(assuming the contract is correct)
at: eval:17:0
Added in version 0.6 of package scramble-lib.
procedure
(convert/ic convert [ #:name name] #:exn->lines exn->lines) → impersonator-contract? convert : (-> any/c any/c) name : any/c = '(convert/ic ....) exn->lines : (lambda (exn) ....)
The convert procedure should be idempotent; that is, (convert (convert value)) should be equal to (convert value).
The exn->lines function must produce a string suitable for adding to the end of a well-formed error message, such as "" or "\n error: went wrong". The default exn->lines produces "\n error: " followed by the first line of the exception’s message, plus "..." if the message was truncated.
> (define (to-string v) (cond [(string? v) v] [(bytes? v) (bytes->string/utf-8 v)] [(symbol? v) (symbol->string v)] [else (error 'to-string "cannot convert to string\n given: ~e" v)]))
> (define stringable/ic (convert/ic to-string #:name 'stringable/ic))
> (define/contract concat (-> (listof stringable/ic) string?) (lambda (strs) (apply string-append strs))) > (concat (list "a" #"b" 'c)) "abc"
> (concat (list "a" #"b" 5)) concat: contract violation
expected: stringable/ic
given: 5
error: to-string: cannot convert to string...
in: an element of
the 1st argument of
(-> (listof stringable/ic) string?)
contract from: (definition concat)
blaming: top-level
(assuming the contract is correct)
at: eval:24:0