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add for/sum', for/product', etc.

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This commit is contained in:
Matthew Flatt 2011-07-25 15:12:04 -04:00
parent c6f1178be3
commit f1160da419
3 changed files with 51 additions and 0 deletions
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16
collects/racket/private/for.rkt
View File

@ -21,6 +21,10 @@
for/or for*/or
for/first for*/first
for/last for*/last
for/sum for*/sum
(rename for/sum Σ) (rename for*/sum Σ*)
for/product for*/product
(rename for/product ∏) (rename for*/product ∏*)
for/hash for*/hash
for/hasheq for*/hasheq
for/hasheqv for*/hasheqv
@ -1437,6 +1441,18 @@
(lambda (rhs) rhs)
(lambda (x) x))
(define-for-variants (for/sum for*/sum)
([result 0])
(lambda (x) x)
(lambda (rhs) rhs)
(lambda (x) #`(+ result #,x)))
(define-for-variants (for/product for*/product)
([result 1])
(lambda (x) x)
(lambda (rhs) rhs)
(lambda (x) #`(* result #,x)))
(define-for-variants (for/hash for*/hash)
([table #hash()])
(lambda (x) x)

31
collects/scribblings/reference/for.scrbl
View File

@ -161,6 +161,33 @@ result of the @racket[for/or] expression is
(error "doesn't get here"))
]}
@deftogether[(
@defform[(for/sum (for-clause ...) body ...+)]
@defform[(Σ (for-clause ...) body ...+)]
)]{
Iterates like @racket[for], but each result of the last @racket[body]
is accumulated into a result with @racket[+].
@examples[
(for/sum ([i '(1 2 3 4)]) i)
(Σ ([i (in-range 100)]) i)
]}
@deftogether[(
@defform[(for/product (for-clause ...) body ...+)]
@defform[(∏ (for-clause ...) body ...+)]
)]{
Iterates like @racket[for], but each result of the last @racket[body]
is accumulated into a result with @racket[*].
@examples[
(for/product ([i '(1 2 3 4)]) i)
(∏ ([i (in-range 1 5)]) i)
]}
@defform[(for/lists (id ...) (for-clause ...) body ...+)]{
@ -240,6 +267,10 @@ nested.
@defform[(for*/hasheqv (for-clause ...) body ...+)]
@defform[(for*/and (for-clause ...) body ...+)]
@defform[(for*/or (for-clause ...) body ...+)]
@defform[(for*/sum (for-clause ...) body ...+)]
@defform[(Σ* (for-clause ...) body ...+)]
@defform[(for*/product (for-clause ...) body ...+)]
@defform[(∏* (for-clause ...) body ...+)]
@defform[(for*/first (for-clause ...) body ...+)]
@defform[(for*/last (for-clause ...) body ...+)]
@defform[(for*/fold ([accum-id init-expr] ...) (for-clause ...) body ...+)]

4
collects/tests/racket/for-util.rkt
View File

@ -64,6 +64,10 @@
(test (list (for/last ([i gen]) i)) 'gen (for/and ([i gen]) (member i `seq)))
(test `seq 'gen (for/or ([i gen]) (member i `seq)))
(test (for/first ([i gen]) i) 'gen (for/or ([i gen]) (and (member i `seq) i)))
(test (for/sum ([i gen]) (if (number? i) i 0)) 'gen
(for/fold ([n 0]) ([i gen]) (if (number? i) (+ i n) n)))
(test (for/product ([i gen]) (if (number? i) i 1)) 'gen
(for/fold ([n 1]) ([i gen]) (if (number? i) (* i n) n)))
(test #t 'gen (for/and ([(i k) (in-parallel gen `seq)])
(equal? i k)))
(test #f 'gen (for/and ([i gen])