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added a nullary case to compose

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svn: r14697
This commit is contained in:
Eli Barzilay 2009-05-03 20:41:37 +00:00
parent a1b65fb055
commit a1d943146b
3 changed files with 5 additions and 2 deletions
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3
collects/scheme/private/list.ss
View File

@ -232,7 +232,7 @@
(define compose (define compose
(case-lambda (case-lambda
[(f) (if (procedure? f) [(f) (if (procedure? f)
f f
(raise-type-error 'compose "procedure" f))] (raise-type-error 'compose "procedure" f))]
[(f g) [(f g)
@ -247,6 +247,7 @@
(call-with-values (lambda () (g a)) f)) (call-with-values (lambda () (g a)) f))
(lambda args (lambda args
(call-with-values (lambda () (apply g args)) f)))))] (call-with-values (lambda () (apply g args)) f)))))]
[() values]
[(f . more) [(f . more)
(if (procedure? f) (if (procedure? f)
(let ([m (apply compose more)]) (let ([m (apply compose more)])

3
collects/scribblings/reference/procedures.scrbl
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@ -38,7 +38,8 @@ Returns a procedure that composes the given functions, applying the
last @scheme[proc] first and the first @scheme[proc] last. The last @scheme[proc] first and the first @scheme[proc] last. The
composed functions can consume and produce any number of values, as composed functions can consume and produce any number of values, as
long as each function produces as many values as the preceding long as each function produces as many values as the preceding
function consumes. function consumes. When no @scheme[proc] arguments are given, the
result is @scheme[values].
@mz-examples[ @mz-examples[
((compose - sqrt) 10) ((compose - sqrt) 10)

1
collects/tests/mzscheme/function.ss
View File

@ -14,6 +14,7 @@
(test 'hi (compose (case-lambda [(x) 'bye][(y z) 'hi]) (lambda () (values 1 2)))) (test 'hi (compose (case-lambda [(x) 'bye][(y z) 'hi]) (lambda () (values 1 2))))
(test 'ok (compose (lambda () 'ok) (lambda () (values)))) (test 'ok (compose (lambda () 'ok) (lambda () (values))))
(test 'ok (compose (lambda () 'ok) (lambda (w) (values))) 5) (test 'ok (compose (lambda () 'ok) (lambda (w) (values))) 5)
(test 0 (compose) 0)
(test-values '(1 2 3) (lambda () ((compose (lambda (x) (values x (add1 x) (+ x 2))) (lambda (y) y)) 1))) (test-values '(1 2 3) (lambda () ((compose (lambda (x) (values x (add1 x) (+ x 2))) (lambda (y) y)) 1)))
(err/rt-test (compose 5)) (err/rt-test (compose 5))