Certification of Algorithm 35: Sieve
J. S. Hillmore · Communications of the ACM · 1962
v a l u e n, x0, y0; i n t e g e r n; a r r a y x, y; r e a l x0, y0; c o m m e n t if t h e p o i n t s (x[i], y[i]) (i = 1, 2 , -. ., n) a r e --i n this cyclic o r d e r --t h e vertices of a simple closed p o l y g o n a n d (x0, y0) is a p o i n t n o t on a n y side of t h e polygon, t h e n t h e procedure d e t e r m i n e s , b y s e t t i n g " p o i n t in p o l y g o n " to t r u e , w h e t h e r (x0, y0) lies in t h e interior of t h e p o l y g o n ; b e g i n i n t e g e r i; B o o l e a n b;x [ n + l ] : = x [ 1 ] ; y [ n + l ] : = y [ 1 ] ; b : = t r u e ; f o r i i= 1 s t e p 1 u n t i l n d o