#! /usr/bin/env python
#
def segment_point_dist ( p1, p2, p ):

#*****************************************************************************80
#
## SEGMENT_POINT_DIST: distance ( line segment, point ).
#
#  Discussion:
#
#    A line segment is the finite portion of a line that lies between
#    two points.
#
#    The nearest point will satisfy the condition
#
#      PN = (1-T) * P1 + T * P2.
#
#    T will always be between 0 and 1.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    18 October 2015
#
#  Author:
#
#    John Burkardt
#
#  Parameters:
#
#    Input, real P1(2), P2(2), the endpoints of the line segment.
#
#    Input, real P(2), the point whose nearest neighbor on the line
#    segment is to be determined.
#
#    Output, real DIST, the distance from the point to the line segment.
#
  import numpy as np
#
#  If the line segment is actually a point, then the answer is easy.
#
  if ( p1[0] == p2[0] and p1[1] == p2[1] ):

    t = 0.0

  else:

    bot = ( p2[0] - p1[0] ) ** 2 + ( p2[1] - p1[1] ) ** 2

    t = ( ( p[0] - p1[0] ) * ( p2[0] - p1[0] ) \
        + ( p[1] - p1[1] ) * ( p2[1] - p1[1] ) ) / bot

    t = max ( t, 0.0 )
    t = min ( t, 1.0 )

  pn = np.zeros ( 2 )

  pn[0] = p1[0] + t * ( p2[0] - p1[0] )
  pn[1] = p1[1] + t * ( p2[1] - p1[1] )

  dist = np.sqrt ( ( pn[0] - p[0] ) ** 2 + ( pn[1] - p[1] ) ** 2 )

  return dist