1 ! Copyright (C) 2007 Slava Pestov.
2 ! See http://factorcode.org/license.txt for BSD license.
3 USING: kernel math math.functions ;
6 : monic ( c b a -- c' b' ) tuck / >r / r> ;
8 : discriminant ( c b -- b d ) tuck sq 4 / swap - sqrt ;
10 : critical ( b d -- -b/2 d ) >r -2 / r> ;
12 : +- ( x y -- x+y x-y ) [ + ] 2keep - ;
14 : quadratic ( c b a -- alpha beta )
15 #! Solve a quadratic equation ax^2 + bx + c = 0
16 monic discriminant critical +- ;
18 : qeval ( x c b a -- y )
19 #! Evaluate ax^2 + bx + c
20 >r pick * r> roll sq * + + ;