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Fixed https://github.com/soegaard/bracket/issues/8

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This commit is contained in:
Jens Axel Søgaard 2013-04-07 21:33:20 +02:00
parent c3acce9bab
commit f68eb51365
1 changed files with 10 additions and 6 deletions
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16
bracket/bracket.rkt
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@ -74,7 +74,8 @@
(define (holdable? o)
(and (symbol? o)
(memq o '(Hold))))
(eq? o 'Hold)
#;(memq o '(Hold))))
; In the BRACKET language an application of
; a non-function evaluates to an expression.
@ -886,14 +887,17 @@
true]
[else (construct 'Equal (list u1 u2))]))
(define (Expand u)
(define (Expand u)
; [Cohen, Elem, p.253]
(case (kind u)
[(Plus)
(define v (Operand u 0))
#;(displayln (list u '=> v (Minus u v)))
(Plus (Expand v)
(Expand (Minus u v)))]
; (displayln (list u '=> v (Minus u v)))
(apply Plus (map Expand (operands u)))
; This: (Plus (Expand v) (Expand (Minus u v)))
; is used in [Cohen] but leads to an infinite loop
; when expanding (Plus 1 a (Times -1 (Plus 1 a)) x)
]
[(Times)
(define v (Operand u 0))
#;(Fix-point ; TODO: neeeded ?
@ -906,7 +910,7 @@
(Expand-product (Expand v)
(Expand (Quotient u v))))
(Expand-product (Expand v)
(Expand (Quotient u v)))]
(Expand (Quotient u v)))]
[(Power)
(define base (Operand u 0))
(define exponent (Operand u 1))