Implement Polyhedron.fromstring

[linpy.git] / pypol / linear.py

diff --git a/pypol/linear.py b/pypol/linear.py
index 3939c71..0712e1e 100644 (file)
--- a/pypol/linear.py
+++ b/pypol/linear.py
@@ -1,5 +1,7 @@
+import ast
 import functools
 import numbers
+import re
 
 from fractions import Fraction, gcd
 
@@ -86,9 +88,38 @@ class Expression:
         self._dimension = len(self._symbols)
         return self
 
+    @classmethod
+    def _fromast(cls, node):
+        if isinstance(node, ast.Module):
+            assert len(node.body) == 1
+            return cls._fromast(node.body[0])
+        elif isinstance(node, ast.Expr):
+            return cls._fromast(node.value)
+        elif isinstance(node, ast.Name):
+            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.BinOp):
+            left = cls._fromast(node.left)
+            right = cls._fromast(node.right)
+            if isinstance(node.op, ast.Add):
+                return left + right
+            elif isinstance(node.op, ast.Sub):
+                return left - right
+            elif isinstance(node.op, ast.Mult):
+                return left * right
+            elif isinstance(node.op, ast.Div):
+                return left / right
+        raise SyntaxError('invalid syntax')
+
     @classmethod
     def fromstring(cls, string):
-        raise NotImplementedError
+        string = re.sub(r'(\d+|\))\s*([^\W\d_]\w*|\()', r'\1*\2', string)
+        tree = ast.parse(string, 'eval')
+        return cls._fromast(tree)
 
     @property
     def symbols(self):
@@ -412,7 +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):
@@ -579,7 +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)
@@ -587,7 +651,7 @@ class Polyhedron:
         return bset
 
     @classmethod
-    def _fromisl(cls, bset):
+    def _fromisl(cls, bset, symbols):
         raise NotImplementedError
         equalities = ...
         inequalities = ...
@@ -602,9 +666,7 @@ Empty = eq(0,1)
 Universe = Polyhedron()
 
 if __name__ == '__main__':
-    e1 = Expression(coefficients={'a': 2, 'b': 2}, constant= 1)
-    p1 = Polyhedron(equalities=[e1]) # empty
-    e2 = Expression(coefficients={'x': 3, 'y': 2}, constant= 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())