add geometry distance and angle function

src/geometry.py

@@ -2,7 +2,7 @@
 # -*- coding: utf-8 -*-
 """2D geometry objects.
 
-:Date: 2019-08-20
+:Date: 2019-08-28
 
 .. module:: geometry
   :platform: *nix, Windows
@@ -14,6 +14,36 @@ import math
 import numpy as np
 
 
+def distance(point1, point2):
+  """Distance between two points (or length of a straight line).
+
+  :param point1: first point (first end point of straight line)
+  :type point1: tuple
+  :param point2: second point (second end point of straight line)
+  :type point2: tuple
+
+  :returns: distance between the two points
+  :rtype: float
+  """
+  return math.sqrt((point2[0]-point1[0])**2 + (point2[1]-point1[1])**2)
+
+
+def angle(point1, point2=None):
+  """Angle of point or between two points.
+
+  :param point1: (first) point
+  :type point1: tuple
+  :param point2: second point (default = None)
+  :type point2: tuple
+
+  :returns: angle of point or between two points
+  :rtype: float
+  """
+  if point2 is None:
+    return math.atan2(point1[1], point1[0])
+  return math.atan2(point2[1]-point1[1], point2[0]-point1[0])
+
+
 def translate(vec, *pts):
   """Translate a point or polygon by a given vector.
 
@@ -281,7 +311,7 @@ def cubics(pts, **kwargs):
       if 'global_deformation' in kwargs:
         lr = [(pts[l-kwargs['index_offset']],
                pts[r-kwargs['index_offset']]) for l, r in kwargs['inc']]
-        ang = [math.atan2(r[1]-l[1], r[0]-l[0]) for l, r in lr]
+        ang = [angle(l, r) for l, r in lr]
         # system deformation
         U = kwargs['global_deformation']
         if 'rotation_plane' in kwargs and 'xz' == kwargs['rotation_plane']:

src/geometry_plot.py

@@ -12,7 +12,9 @@
 """
 import math
 import pylab
-from geometry import line, interpolate_hermite, rotate_xy, translate_xy
+from geometry import (
+  distance, angle, line, interpolate_hermite, rotate_xy, translate_xy
+)
 
 pylab.style.use('dark_background')
 pylab.rcParams['grid.color'] = 'gray'
@@ -74,8 +76,8 @@ def plot_cubic_lines(lns, **kwargs):
 
   for ln in lns:
     l, r, d = ln
-    L = math.sqrt((r[0]-l[0])**2 + (r[1]-l[1])**2)
-    ang = math.atan2(r[1]-l[1], r[0]-l[0])
+    L = distance(l, r)
+    ang = angle(l, r)
     x, y = interpolate_hermite(d[1], d[2], d[4], d[5], d[0], d[3],
                                scale_x=L, scale_y=factor, samples=samples)
     x, y = rotate_xy((0, 0), ang, x, y)