rotate-point ( pt angle -- pt' )


Vocabulary
boids

Inputs
ptan object
anglean object


Outputs
pt'an object


Definition
USING: arrays math math.functions sequences ;

IN: boids

:: rotate-point ( pt angle -- pt' )
pt first :> x pt second :> y angle cos :> c angle sin :> s x
c * y s * - x s * y c * + 2array ;