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Demonstrates conda for first-match-wins dispatch over a set of rewrite rules: 0+x = x, x+0 = x, 0*y = 0, x*0 = 0, 1*x = x, x*1 = x, default unchanged. Six rules + a fall-through default, all wrapped in a single conda. The first clause whose head succeeds commits to that rewrite. The fall- through default ensures the relation always succeeds with at least the unchanged input. 6 new tests, 521/521 cumulative.
48 lines
1.2 KiB
Plaintext
48 lines
1.2 KiB
Plaintext
;; lib/minikanren/tests/simplifyo.sx — algebraic expression simplifier
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;; demo using conda for first-match-wins dispatch.
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(define
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simplify-step-o
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(fn
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(expr result)
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(conda
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((fresh (x) (== expr (list :+ 0 x)) (== result x)))
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((fresh (x) (== expr (list :+ x 0)) (== result x)))
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((fresh (y) (== expr (list :* 0 y)) (== result 0)))
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((fresh (x) (== expr (list :* x 0)) (== result 0)))
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((fresh (x) (== expr (list :* 1 x)) (== result x)))
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((fresh (x) (== expr (list :* x 1)) (== result x)))
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((== result expr))))) ;; default: unchanged
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(mk-test
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"simplify-zero-plus"
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(run* q (simplify-step-o (list :+ 0 :y) q))
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(list :y))
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(mk-test
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"simplify-plus-zero"
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(run* q (simplify-step-o (list :+ :x 0) q))
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(list :x))
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(mk-test
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"simplify-zero-times"
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(run* q (simplify-step-o (list :* 0 :y) q))
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(list 0))
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(mk-test
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"simplify-one-times"
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(run* q (simplify-step-o (list :* 1 :y) q))
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(list :y))
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(mk-test
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"simplify-no-rule-applies"
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(run* q (simplify-step-o (list :+ :x :y) q))
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(list (list :+ :x :y)))
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(mk-test
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"simplify-non-identity-form"
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(run* q (simplify-step-o (list :+ 5 7) q))
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(list (list :+ 5 7)))
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(mk-tests-run!)
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