add Sketch.solve(), in progress

Sketch.py

@@ -1,4 +1,7 @@
 
+from numpy import *
+from openopt import SLE
+
 class Sketch(object):
     def __init__(self):
         self.shapes = []
@@ -9,3 +12,28 @@ class Sketch(object):
 
     def __contains__(self, item):
         return self.shapes.__contains__(item)
+
+    def solve(self):
+        shape_vars = {}
+        varid = 0
+        equations = []
+        for c in self.constraints:
+            equations += c.toEqu()
+        for e in equations:
+            coeffs = e[0]
+            for c in coeffs:
+                shape_var = c[1]
+                if not shape_var in shape_vars:
+                    shape_vars[shape_var] = varid
+                    varid += 1
+        C = empty((len(equations), len(shape_vars)))
+        d = empty(len(equations))
+        for i in range(len(equations)):
+            e = equations[i]
+            coeffs = e[0]
+            for c in coeffs:
+                var_index = shape_vars[coeffs[1]]
+                C[i][var_index] = coeffs[0]
+            d[i] = e[1]
+        s = SLE(C, d)
+        r = s.solve()