Implement Polyhedron.fromstring

[linpy.git] / pypol / linear.py

diff --git a/pypol/linear.py b/pypol/linear.py
index 8a61744..0712e1e 100644 (file)
--- a/pypol/linear.py
+++ b/pypol/linear.py
@@ -117,9 +117,7 @@ class Expression:
 
     @classmethod
     def fromstring(cls, string):
-        string = re.sub(r'(\d+|\))\s*([^\W\d_]\w*|\()',
-                lambda m: '{}*{}'.format(m.group(1), m.group(2)),
-                string)
+        string = re.sub(r'(\d+|\))\s*([^\W\d_]\w*|\()', r'\1*\2', string)
         tree = ast.parse(string, 'eval')
         return cls._fromast(tree)
 
@@ -445,7 +443,40 @@ class Polyhedron:
 
     @classmethod
     def fromstring(cls, string):
-        raise NotImplementedError
+        string = string.strip()
+        string = re.sub(r'^\{\s*|\s*\}$', '', string)
+        string = re.sub(r'([^<=>])=([^<=>])', r'\1==\2', string)
+        string = re.sub(r'(\d+|\))\s*([^\W\d_]\w*|\()', r'\1*\2', string)
+        equalities = []
+        inequalities = []
+        for cstr in re.split(r',|;|and|&&|/\\|∧', string, flags=re.I):
+            tree = ast.parse(cstr.strip(), 'eval')
+            if not isinstance(tree, ast.Module) or len(tree.body) != 1:
+                raise SyntaxError('invalid syntax')
+            node = tree.body[0]
+            if not isinstance(node, ast.Expr):
+                raise SyntaxError('invalid syntax')
+            node = node.value
+            if not isinstance(node, ast.Compare):
+                raise SyntaxError('invalid syntax')
+            left = Expression._fromast(node.left)
+            for i in range(len(node.ops)):
+                op = node.ops[i]
+                right = Expression._fromast(node.comparators[i])
+                if isinstance(op, ast.Lt):
+                    inequalities.append(right - left - 1)
+                elif isinstance(op, ast.LtE):
+                    inequalities.append(right - left)
+                elif isinstance(op, ast.Eq):
+                    equalities.append(left - right)
+                elif isinstance(op, ast.GtE):
+                    inequalities.append(left - right)
+                elif isinstance(op, ast.Gt):
+                    inequalities.append(left - right - 1)
+                else:
+                    raise SyntaxError('invalid syntax')
+                left = right
+        return cls(equalities, inequalities)
 
     @property
     def equalities(self):
@@ -612,7 +643,7 @@ class Polyhedron:
                 dim = symbols.index(symbol)
                 cin = libisl.isl_constraint_set_coefficient_val(cin, libisl.isl_dim_set, dim, val)
             if inequality.constant != 0:
-                val = str(ineq.constant).encode()
+                val = str(inequality.constant).encode()
                 val = libisl.isl_val_read_from_str(_main_ctx, val)
                 cin = libisl.isl_constraint_set_constant_val(cin, val)
             bset = libisl.isl_basic_set_add_constraint(bset, cin)
@@ -635,9 +666,7 @@ Empty = eq(0,1)
 Universe = Polyhedron()
 
 if __name__ == '__main__':
-    e1 = Expression('2a + 2b + 1')
-    p1 = Polyhedron(equalities=[e1]) # empty
-    e2 = Expression('3x + 2y + 3')
-    p2 = Polyhedron(equalities=[e2]) # not empty
+    p1 = Polyhedron('2a + 2b + 1 == 0') # empty
     print(p1._toisl())
+    p2 = Polyhedron('3x + 2y + 3 == 0') # not empty
     print(p2._toisl())