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original commit: 89756069b913e24574b536f36f9ec87803985644
This commit is contained in:
Matthew Flatt 1997-09-10 12:56:54 +00:00
parent 838b443062
commit 84f81ab101
1 changed files with 16 additions and 9 deletions
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25
collects/mzlib/functior.ss
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@ -7,16 +7,23 @@
(define compose
(polymorphic
(case-lambda
[(f) f]
[(f) (if (procedure? f) f (raise-type-error 'compose "procedure" f))]
[(f g)
(if (eqv? 1 (arity f)) ; optimize: don't use call-w-values
(if (eqv? 1 (arity g)) ; optimize: single arity everywhere
(lambda (x) (f (g x)))
(lambda args (f (apply g args))))
(lambda args
(call-with-values
(lambda () (apply g args))
f)))]
(let ([f (compose f)]
[g (compose g)])
(if (eqv? 1 (arity f)) ; optimize: don't use call-w-values
(if (eqv? 1 (arity g)) ; optimize: single arity everywhere
(lambda (x) (f (g x)))
(lambda args (f (apply g args))))
(if (eqv? 1 (arity g)) ; optimize: single input
(lambda (a)
(call-with-values
(lambda () (g a))
f))
(lambda args
(call-with-values
(lambda () (apply g args))
f)))))]
[(f . more)
(let ([m (apply compose more)])
(compose f m))])))