Improve Polyhedron.fromstring

[linpy.git] / pypol / linear.py

diff --git a/pypol/linear.py b/pypol/linear.py
index 524b3cb..8fdece9 100644 (file)
--- a/pypol/linear.py
+++ b/pypol/linear.py
@@ -54,7 +54,7 @@ class Expression:
         '_coefficients',
         '_constant',
         '_symbols',
-        '_dimension'
+        '_dimension',
     )
 
     def __new__(cls, coefficients=None, constant=0):
@@ -97,8 +97,7 @@ class Expression:
 
     @classmethod
     def _fromast(cls, node):
-        if isinstance(node, ast.Module):
-            assert len(node.body) == 1
+        if isinstance(node, ast.Module) and len(node.body) == 1:
             return cls._fromast(node.body[0])
         elif isinstance(node, ast.Expr):
             return cls._fromast(node.value)
@@ -106,9 +105,8 @@ class Expression:
             return Symbol(node.id)
         elif isinstance(node, ast.Num):
             return Constant(node.n)
-        elif isinstance(node, ast.UnaryOp):
-            if isinstance(node.op, ast.USub):
-                return -cls._fromast(node.operand)
+        elif isinstance(node, ast.UnaryOp) and isinstance(node.op, ast.USub):
+            return -cls._fromast(node.operand)
         elif isinstance(node, ast.BinOp):
             left = cls._fromast(node.left)
             right = cls._fromast(node.right)
@@ -362,6 +360,10 @@ class Constant(Expression):
 
 class Symbol(Expression):
 
+    __slots__ = Expression.__slots__ + (
+        '_name',
+    )
+
     def __new__(cls, name):
         if isinstance(name, Symbol):
             name = name.name
@@ -421,7 +423,7 @@ class Polyhedron:
         '_equalities',
         '_inequalities',
         '_constraints',
-        '_symbols'
+        '_symbols',
     )
 
     def __new__(cls, equalities=None, inequalities=None):
@@ -456,23 +458,20 @@ class Polyhedron:
         return self
 
     @classmethod
-    def fromstring(cls, string):
-        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')
+    def _fromast(cls, node):
+        if isinstance(node, ast.Module) and len(node.body) == 1:
+            return cls._fromast(node.body[0])
+        elif isinstance(node, ast.Expr):
+            return cls._fromast(node.value)
+        elif isinstance(node, ast.BinOp) and isinstance(node.op, ast.BitAnd):
+            equalities1, inequalities1 = cls._fromast(node.left)
+            equalities2, inequalities2 = cls._fromast(node.right)
+            equalities = equalities1 + equalities2
+            inequalities = inequalities1 + inequalities2
+            return equalities, inequalities
+        elif isinstance(node, ast.Compare):
+            equalities = []
+            inequalities = []
             left = Expression._fromast(node.left)
             for i in range(len(node.ops)):
                 op = node.ops[i]
@@ -488,8 +487,23 @@ class Polyhedron:
                 elif isinstance(op, ast.Gt):
                     inequalities.append(left - right - 1)
                 else:
-                    raise SyntaxError('invalid syntax')
+                    break
                 left = right
+            else:
+                return equalities, inequalities
+        raise SyntaxError('invalid syntax')
+
+    @classmethod
+    def fromstring(cls, string):
+        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)
+        tokens = re.split(r',|;|and|&&|/\\|∧', string, flags=re.I)
+        tokens = ['({})'.format(token) for token in tokens]
+        string = ' & '.join(tokens)
+        tree = ast.parse(string, 'eval')
+        equalities, inequalities = cls._fromast(tree)
         return cls(equalities, inequalities)
 
     @property
@@ -677,8 +691,10 @@ class Polyhedron:
             { [i0, i1] : 2i1 >= -2 - i0 } '''
 
 Empty = eq(0,1)
+
 Universe = Polyhedron()
 
+
 if __name__ == '__main__':
     p1 = Polyhedron('2a + 2b + 1 == 0') # empty
     print(p1._toisl())