16 lines
378 B
Factor
16 lines
378 B
Factor
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! Copyright (C) 2019-2020 KUSUMOTO Norio.
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! See http://factorcode.org/license.txt for BSD license.
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USING: factlog kernel assocs math ;
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IN: factlog.examples.factorial
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LOGIC-PREDS: factorial ;
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LOGIC-VARS: N F N2 F2 ;
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{ factorial N F } {
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{ (>) N 0 }
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[ [ N of 1 - ] N2 is ]
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{ factorial N2 F2 }
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[ [ [ F2 of ] [ N of ] bi * ] F is ] !!
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} rule
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{ factorial 0 1 } fact
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