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Unparse now display products with negative powers as fractions.

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This commit is contained in:
Jens Axel Søgaard 2012-07-05 19:59:05 +02:00
parent 034cd321f6
commit 0538280d65
2 changed files with 31 additions and 7 deletions
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11
bracket/bracket.rkt
View File

@ -618,7 +618,7 @@
(define (simplify-minus ops)
(define (simplify-minus ops)
; - unary and binary does not occur in simplified expressions
; - (Minus x) => (Times -1 x)
; - (Minus a b) => (Plus a (Times -1 b))
@ -861,6 +861,7 @@
(concurrent-substitute u ts rs))
(define (Equal u1 u2)
(displayln (list 'Equal u1 u2))
(cond
[(and (number? u1) (number? u2))
(= u1 u2)]
@ -868,9 +869,12 @@
(string=? u1 u2)]
[(equal? u1 u2)
true]
#;[(equal? (Expand (Minus u1 u2)) 0)
true]
[else (construct 'Equal (list u1 u2))]))
(define (Expand u)
(displayln u)
; [Cohen, Elem, p.253]
(case (kind u)
[(Plus)
@ -887,7 +891,9 @@
[(power-expression? u) (Expand-power u)]
[else u]))
(Expand-product (Expand v)
(Expand (Quotient u v))))]
(Expand (Quotient u v))))
#;(Expand-product (Expand v)
(Expand (Quotient u v)))]
[(Power)
(define base (Operand u 0))
(define exponent (Operand u 1))
@ -1424,6 +1430,7 @@
(check-equal? (Match-linear-form (Plus 3 x y) x) (List 1 (Plus 3 y)))
; List:
; Equal:
;(check-equal? (Equal (Power (Minus x 1) 2) (Plus (Power x 2) (Times -2 x) 1)) true)
;;; Solve
(require (submod ".." solve))

27
bracket/unparse.rkt
View File

@ -6,7 +6,8 @@
(provide unparse)
(require (submod "bracket.rkt" expression-core)
(submod "bracket.rkt" equation-expression))
(submod "bracket.rkt" equation-expression)
(submod "bracket.rkt" bracket))
(define (map/first? base f xs)
@ -55,10 +56,23 @@
[(eqv? (first ops) -1)
(string-append "-" (unparse-product (cons 'Times (rest ops))))]
[else
(define unwrapped
(string-append* (add-between (map unparse-factor ops) "*")))
(wrap-if (and level-below-times? (>= (length ops) 2))
unwrapped)])]
(define-values (den num)
(partition (λ (f) (and (power-expression? f)
(number? (exponent f))
(negative? (exponent f))))
ops))
(set! den (map (λ (f) (Power (base f) (- (exponent f)))) den))
(define (format-factors ops)
(define unwrapped
(string-append* (add-between (map unparse-factor ops) "*")))
(wrap-if (and level-below-times? (>= (length ops) 2))
unwrapped))
(if (empty? den)
(format-factors num)
(format "~a/~a"
(format-factors num)
(wrap-if (>= (length den) 2)
(unparse (apply Times den)))))])]
[else
(unparse-factor form first?)]))
@ -148,6 +162,9 @@
(check-equal? (unparse '(Times -2 x)) "-2*x")
; Products of products (unsimplified)
(check-equal? (unparse '(Times 2 (Times 3 x) (Times -5 y))) "2*(3*x)*(-5*y)")
; Products with factors with negative exponents
(check-equal? (unparse (Quotient x y)) "x/y")
(check-equal? (unparse (Quotient x (Times y z))) "x/(y*z)")
; Powers
(check-equal? (unparse '(Power 2 3)) "2^3")
(check-equal? (unparse '(Power -2 3)) "(-2)^3")