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Fix for/sum: when summing something other than integers.

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original commit: 94175034925dc2aff57cde2ccea6fb465cff6b98
This commit is contained in:
Vincent St-Amour 2011-12-01 17:35:35 -05:00
parent a68be65d3e
commit bace1be6d5
1 changed files with 27 additions and 2 deletions
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29
collects/typed-racket/base-env/prims.rkt
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@ -642,7 +642,6 @@ This file defines two sorts of primitives. All of them are provided into any mod
(for/last: for/last)
(for/vector: for/vector)
(for/flvector: for/flvector)
(for/sum: for/sum)
(for/product: for/product))
;; Unlike with the above, the inferencer can handle any number of #:when
@ -694,6 +693,7 @@ This file defines two sorts of primitives. All of them are provided into any mod
'type-ascription
#'(values var.ty ...))]))
(define-syntax (for*: stx)
(syntax-parse stx #:literals (:)
[(_ (~seq : Void) ...
@ -733,7 +733,6 @@ This file defines two sorts of primitives. All of them are provided into any mod
(for*/last: for*/last)
(for*/vector: for*/vector)
(for*/flvector: for*/flvector)
(for*/sum: for*/sum)
(for*/product: for*/product))
;; Like for/lists: and for/fold:, the inferencer can handle these correctly.
@ -784,6 +783,32 @@ This file defines two sorts of primitives. All of them are provided into any mod
'type-ascription
#'(values var.ty ...))]))
(define-for-syntax (define-for/sum:-variant for/folder)
(lambda (stx)
(syntax-parse stx #:literals (:)
[(_ : ty
(clause:for-clause ...)
c:expr ...)
;; ty has to include exact 0, the initial value of the accumulator
;; (to be consistent with Racket semantics).
;; We can't just change the initial value to be 0.0 if we expect a
;; Float result. This is problematic in some cases e.g:
;; (for/sum: : Float ([i : Float '(1.1)] #:when (zero? (random 1))) i)
(quasisyntax/loc stx
(#,for/folder : ty ([acc : ty 0])
(clause.expand ... ...)
(let ([new (let () c ...)])
(+ acc new))))])))
(define-syntax (define-for/sum:-variants stx)
(syntax-parse stx
[(_ (name for/folder) ...)
(quasisyntax/loc stx
(begin (define-syntax name (define-for/sum:-variant #'for/folder))
...))]))
(define-for/sum:-variants (for/sum: for/fold:) (for*/sum: for*/fold:))
(define-syntax (provide: stx)
(syntax-parse stx
[(_ [i:id t] ...)