Hi all,
Here is the cross product from math.matrices;
=======================================
: cross-i ( vec1 vec2 -- i )
over third over second * >r
swap second swap third * r> - ;
: cross-j ( vec1 vec2 -- j )
over first over third * >r
swap third swap first * r> - ;
: cross-k ( vec1 vec2 -- k )
over first over second * >r
swap second swap first * r> - ;
: cross ( vec1 vec2 -- vec3 )
[ cross-i ] 2keep [ cross-j ] 2keep cross-k 3array ;
=======================================
Here is a cleaned up version that uses Eduardo's cleave combinators; the
combinators structure the stack flow and make the inherent symmetry of
the cross product definition more visible:
=======================================
<PRIVATE
: x first ; inline
: y second ; inline
: z third ; inline
: i [ [ y ] [ z ] bi* * ] [ [ z ] [ y ] bi* * ] 2bi - ;
: j [ [ z ] [ x ] bi* * ] [ [ x ] [ z ] bi* * ] 2bi - ;
: k [ [ y ] [ x ] bi* * ] [ [ x ] [ y ] bi* * ] 2bi - ;
PRIVATE>
: cross ( vec1 vec2 -- vec3 ) [ i ] [ j ] [ k ] 2tri 3array ;
=======================================
Slava
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