add XDistance and YDistance constraints

XDistance.py

@@ -0,0 +1,20 @@
+
+from Constraint import Constraint
+
+class Vertical(Constraint):
+    def __init__(self, shape1, pt1, shape2, pt2, dist):
+        self.shape1 = shape1
+        self.pt1 = pt1
+        self.shape2 = shape2
+        self.pt2 = pt2
+        self.dist
+
+    def toEqu(self):
+        varrefs1 = self.shape1.toEqu(pt1)[0]
+        varrefs2 = self.shape2.toEqu(pt2)[0]
+        coeffs = []
+        for i in range(len(varrefs1)):
+            coeffs.append((-1 * varrefs1[i], (self.shape1, i)))
+        for i in range(len(varrefs2)):
+            coeffs.append((1 * varrefs2[i], (self.shape2, i))
+        return [(coeffs, self.dist)]

YDistance.py

@@ -0,0 +1,20 @@
+
+from Constraint import Constraint
+
+class Horizontal(Constraint):
+    def __init__(self, shape1, pt1, shape2, pt2, dist):
+        self.shape1 = shape1
+        self.pt1 = pt1
+        self.shape2 = shape2
+        self.pt2 = pt2
+        self.dist = dist
+
+    def toEqu(self):
+        varrefs1 = self.shape1.toEqu(pt1)[1]
+        varrefs2 = self.shape2.toEqu(pt2)[1]
+        coeffs = []
+        for i in range(len(varrefs1)):
+            coeffs.append((-1 * varrefs1[i], (self.shape1, i)))
+        for i in range(len(varrefs2)):
+            coeffs.append((1 * varrefs2[i], (self.shape2, i))
+        return [(coeffs, self.dist)]