21 lines
543 B
Factor
21 lines
543 B
Factor
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! Copyright (C) 2007 Slava Pestov.
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! See http://factorcode.org/license.txt for BSD license.
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USING: kernel math math.functions ;
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IN: quadratic
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: monic ( c b a -- c' b' ) tuck / >r / r> ;
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: discriminant ( c b -- b d ) tuck sq 4 / swap - sqrt ;
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: critical ( b d -- -b/2 d ) >r -2 / r> ;
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: +- ( x y -- x+y x-y ) [ + ] 2keep - ;
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: quadratic ( c b a -- alpha beta )
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#! Solve a quadratic equation ax^2 + bx + c = 0
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monic discriminant critical +- ;
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: qeval ( x c b a -- y )
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#! Evaluate ax^2 + bx + c
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>r pick * r> roll sq * + + ;
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