gistfile1.py

def rayHit(raySeg, polys):
  return minimizeBy([rayIntersectsPoly(raySeg, poly) for poly in polys], lambda(pt => length(pt - raySeg)))

def rayIntersectsPoly(raySeg, poly):
  return minimizeBy([rayIntersectsEdge(raySeg, edge) for edge in poly], lambda(pt => length(pt - raySeg)))

def rayIntersectsEdge(raySeg, edgeSeg):
  pt = intersectLines(raySeg, edgeSeg)
  if lineSegmentContains(edgeSeg, pt) && pointIsInRightDir(raySeg, pt)
  then return pt
  else return Nothing

def intersectLines(seg, seg'):
  dx = seg.end.x - seg.start.x
  dy = seg.end.y - seg.start.y
  dx' = seg'.end.x - seg'.start.x
  dy' = seg'.end.y - seg'.start.y
  x = (dy*dx'*seg.start.x + seg.start.y*dx' - dy'*dx*seg'.start.x) / (dy*dx' - dy'*dx)
  y = (dy/dx) * (x - x1) + y1
  return point(x,y)

def lineSegmentContains(point, seg):
  return bounded(seg.start.x, point.x, seg.end.x) && bounded(seg.start.y, point.y, seg.end.y)

def bounded(x, y, z):
  return (x <= y <= z) || (z <= y <= x)

def pointIsInRightDir(raySeg, pt):
  ptVec = pt - raySet.start
  return sign(ptVec.end.x - ptVec.start.x) == sign(raySeg.end.x - raySeg.start.x) &&
         sign(ptVec.end.y - ptVec.start.y) == sign(raySeg.end.y - raySeg.start.y)