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diff --git a/mesh_tiny_cad/cad_module.py b/mesh_tiny_cad/cad_module.py
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+# ##### BEGIN GPL LICENSE BLOCK #####
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU General Public License
+#  as published by the Free Software Foundation; either version 2
+#  of the License, or (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software Foundation,
+#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+# ##### END GPL LICENSE BLOCK #####
+
+# <pep8 compliant>
+
+
+import bmesh
+
+from mathutils import Vector, geometry
+from mathutils.geometry import intersect_line_line as LineIntersect
+from mathutils.geometry import intersect_point_line as PtLineIntersect
+
+
+class CAD_prefs:
+    VTX_PRECISION = 1.0e-5
+    VTX_DOUBLES_THRSHLD = 0.0001
+
+
+def point_on_edge(p, edge):
+    '''
+    > p:        vector
+    > edge:     tuple of 2 vectors
+    < returns:  True / False if a point happens to lie on an edge
+    '''
+    pt, _percent = PtLineIntersect(p, *edge)
+    on_line = (pt - p).length < CAD_prefs.VTX_PRECISION
+    return on_line and (0.0 <= _percent <= 1.0)
+
+
+def line_from_edge_intersect(edge1, edge2):
+    '''
+    > takes 2 tuples, each tuple contains 2 vectors
+    - prepares input for sending to intersect_line_line
+    < returns output of intersect_line_line
+    '''
+    [p1, p2], [p3, p4] = edge1, edge2
+    return LineIntersect(p1, p2, p3, p4)
+
+
+def get_intersection(edge1, edge2):
+    '''
+    > takes 2 tuples, each tuple contains 2 vectors
+    < returns the point halfway on line. See intersect_line_line
+    '''
+    line = line_from_edge_intersect(edge1, edge2)
+    if line:
+        return (line[0] + line[1]) / 2
+
+
+def test_coplanar(edge1, edge2):
+    '''
+    the line that describes the shortest line between the two edges
+    would be short if the lines intersect mathematically. If this
+    line is longer than the VTX_PRECISION then they are either
+    coplanar or parallel.
+    '''
+    line = line_from_edge_intersect(edge1, edge2)
+    if line:
+        return (line[0] - line[1]).length < CAD_prefs.VTX_PRECISION
+
+
+def closest_idx(pt, e):
+    '''
+    > pt:       vector
+    > e:        bmesh edge
+    < returns:  returns index of vertex closest to pt.
+
+    if both points in e are equally far from pt, then v1 is returned.
+    '''
+    if isinstance(e, bmesh.types.BMEdge):
+        ev = e.verts
+        v1 = ev[0].co
+        v2 = ev[1].co
+        distance_test = (v1 - pt).length <= (v2 - pt).length
+        return ev[0].index if distance_test else ev[1].index
+
+    print("received {0}, check expected input in docstring ".format(e))
+
+
+def closest_vector(pt, e):
+    '''
+    > pt:       vector
+    > e:        2 vector tuple
+    < returns:
+    pt, 2 vector tuple: returns closest vector to pt
+
+    if both points in e are equally far from pt, then v1 is returned.
+    '''
+    if isinstance(e, tuple) and all([isinstance(co, Vector) for co in e]):
+        v1, v2 = e
+        distance_test = (v1 - pt).length <= (v2 - pt).length
+        return v1 if distance_test else v2
+
+    print("received {0}, check expected input in docstring ".format(e))
+
+
+def coords_tuple_from_edge_idx(bm, idx):
+    ''' bm is a bmesh representation '''
+    return tuple(v.co for v in bm.edges[idx].verts)
+
+
+def vectors_from_indices(bm, raw_vert_indices):
+    ''' bm is a bmesh representation '''
+    return [bm.verts[i].co for i in raw_vert_indices]
+
+
+def vertex_indices_from_edges_tuple(bm, edge_tuple):
+    '''
+    > bm:           is a bmesh representation
+    > edge_tuple:   contains two edge indices.
+    < returns the vertex indices of edge_tuple
+    '''
+    def k(v, w):
+        return bm.edges[edge_tuple[v]].verts[w].index
+
+    return [k(i >> 1, i % 2) for i in range(4)]
+
+
+def get_vert_indices_from_bmedges(edges):
+    '''
+    > bmedges:      a list of two bm edges
+    < returns the vertex indices of edge_tuple as a flat list.
+    '''
+    temp_edges = []
+    print(edges)
+    for e in edges:
+        for v in e.verts:
+            temp_edges.append(v.index)
+    return temp_edges
+
+
+def num_edges_point_lies_on(pt, edges):
+    ''' returns the number of edges that a point lies on. '''
+    res = [point_on_edge(pt, edge) for edge in [edges[:2], edges[2:]]]
+    return len([i for i in res if i])
+
+
+def find_intersecting_edges(bm, pt, idx1, idx2):
+    '''
+    > pt:           Vector
+    > idx1, ix2:    edge indices
+    < returns the list of edge indices where pt is on those edges
+    '''
+    if not pt:
+        return []
+    idxs = [idx1, idx2]
+    edges = [coords_tuple_from_edge_idx(bm, idx) for idx in idxs]
+    return [idx for edge, idx in zip(edges, idxs) if point_on_edge(pt, edge)]
+
+
+def duplicates(indices):
+    return len(set(indices)) < 4
+
+
+def vert_idxs_from_edge_idx(bm, idx):
+    edge = bm.edges[idx]
+    return edge.verts[0].index, edge.verts[1].index