'''pointLineDist.py

'''

import math

def pointLineDist(px, py, x0, y0, x1, y1):
  ''' Return (u, v) where u is the fraction of the
      way between the line seg endpoints that the
      perpendicular through P meets the segment.
      and where v is the distance from the point to
      the line.
  '''
  # My approach: translate x0, y0 to the origin.
  x1n = x1-x0
  y1n = y1-y0
  pxn = px-x0
  pyn = py-y0
  # pretend to rotate the line segment to line up with the Y axis.
  hypot = math.sqrt(x1n*x1n+y1n*y1n)
  costheta = y1n / hypot
  sintheta = x1n / hypot
  print "(costheta,sintheta)="+str((costheta,sintheta))
  # apply that rotation to the translated P
  pxnr = costheta*pxn - sintheta*pyn
  pynr = sintheta*pxn + costheta*pyn
  # determine u and v
  u = pynr / hypot
  v = pxnr
  return (u,v)

def test():
  x0 = 1.0
  y0 = 1.0
  x1 = 2.0
  y1 = 2.0
  px = 2.5
  py = 1.0
  print pointLineDist(px,py,x0,y0,x1,y1)

#test()