3 keyword-case-lambda
| (require keyword-lambda/keyword-case-lambda) | |
| package: hash-lambda | |
syntax
(keyword-case-lambda clause ...)
clause = [kw-formals maybe-when body-expr ...+] | [#:args-hash match-pattern maybe-when body-expr ...+] | [#:rest match-pattern maybe-when body-expr ...+] |
[#:kws match-pattern #:kw-args match-pattern #:rest match-pattern maybe-when body-expr ...+] | [_ maybe-when body-expr ...+] | [else maybe-when body-expr ...+] | [#:when condition-expr body-expr ...+] | [#:unless condition-expr body-expr ...+] maybe-when =
| #:when condition-expr | #:unless condition-expr kw-formals = (arg ...) | (arg ... . rest-id) | rest-id arg = id | [id default-expr] | keyword id | keyword [id default-expr]
The kw-formals work just like the kw-formals for lambda.
The #:rest match-pattern clause matches the list of arguments against match-pattern, which can be any pattern that can be used with match (not just an identifier).
The #:args-hash match-pattern clause matches the args-hash against match-pattern, which again can be any pattern that can be used with match.
The #:kws match-pattern #:kw-args match-pattern #:rest match-pattern clause matches the keywords, keyword-arguments, and by-position arguments (from keyword-lambda) against the 3 match-patterns.
The _ and else clauses recive any arguments, including keyword-arguments, but it can still go on to the next clause if the #:when condition is is false (or the #:unless condition is true).
The clauses starting with #:when and #:unless recive any arguments, (including keyword-arguments), but can still go on to the next clause if the #:when condition is false (or the #:unless condition is true).
It also allows you to use #:when and #:unless in the clauses.
keyword-case-lambda does not create a mutable-match-lambda-procedure, but it uses mutable-match-lambda-clause-append (which creates a normal immutable procedure), so it supports going to the next clause with mutable-match-lambda-next. (mutable-keyword-case-lambda creates a mutable-match-lambda-procedure)
> (define f (keyword-case-lambda)) > (procedure-arity f) '()
> (f) f: arity mismatch;
the expected number of arguments does not match the given
number
given: 0
> (define f (keyword-case-lambda [() 0] [(x) 1] [(x y) 2] [args (length args)])) > (f) 0
> (f 1) 1
> (f 1 2) 2
> (f 1 2 3 4 5 6) 6
> (define pythag (keyword-case-lambda [(#:a a #:b b) (sqrt (+ (sqr a) (sqr b)))] [(#:c c #:a a) (sqrt (- (sqr c) (sqr a)))] [(#:c c #:b b) (sqrt (- (sqr c) (sqr b)))] [(#:a a #:b b #:c c) (= (+ (sqr a) (sqr b)) (sqr c))])) > (pythag #:a 3 #:b 4) 5
> (pythag #:c 5 #:a 3) 4
> (pythag #:c 5 #:b 4) 3
> (pythag #:a 3 #:b 4 #:c 5) #t
> (pythag #:a 3 #:b 4 #:c 6) #f
> (define f (keyword-case-lambda [#:args-hash args-hash args-hash])) > (f 0 1 2 #:kw "kw-arg") '#hash((1 . 1) (0 . 0) (2 . 2) (#:kw . "kw-arg"))
> (define f (keyword-case-lambda [#:args-hash (hash-table ['#:m (? number? m)] ['#:v (? number? v)]) `(m: ,m v: ,v)] [(#:mass [m 0] #:velocity [v 0]) #:when (andmap number? (list m v)) `(mass: ,m velocity: ,v)] [#:rest `(m: ,m v: ,v) #:when (andmap number? (list m v)) `(m: ,m v: ,v)] [else (error "error")])) > (f #:m 2 #:v 1) '(m: 2 v: 1)
> (f #:mass 2) '(mass: 2 velocity: 0)
> (f #:mass 2 #:velocity 1) '(mass: 2 velocity: 1)
> (f) '(mass: 0 velocity: 0)
> (f 'm: 2 'v: 1) '(m: 2 v: 1)
> (f "something") error
syntax
(mutable-keyword-case-lambda clause ...)
syntax
(clause->proc/keyword-case-lambda clause)