Improve Expression.fromstring(), Domain.fromstring()

[linpy.git] / pypol / domains.py

diff --git a/pypol/domains.py b/pypol/domains.py
index a34b75b..9bb403e 100644 (file)
--- a/pypol/domains.py
+++ b/pypol/domains.py
@@ -1,8 +1,11 @@
+import ast
 import functools
+import re
 
 from . import islhelper
 
 from .islhelper import mainctx, libisl, isl_set_basic_sets
+from .linexprs import Expression
 
 
 __all__ = [
@@ -242,9 +245,77 @@ class Domain:
             islset1 = libisl.isl_set_union(islset1, islset2)
         return islset1
 
+    @classmethod
+    def _fromast(cls, node):
+        from .polyhedra import Polyhedron
+        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.UnaryOp):
+            domain = cls._fromast(node.operand)
+            if isinstance(node.operand, ast.invert):
+                return Not(domain)
+        elif isinstance(node, ast.BinOp):
+            domain1 = cls._fromast(node.left)
+            domain2 = cls._fromast(node.right)
+            if isinstance(node.op, ast.BitAnd):
+                return And(domain1, domain2)
+            elif isinstance(node.op, ast.BitOr):
+                return Or(domain1, domain2)
+        elif isinstance(node, ast.Compare):
+            equalities = []
+            inequalities = []
+            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:
+                    break
+                left = right
+            else:
+                return Polyhedron(equalities, inequalities)
+        raise SyntaxError('invalid syntax')
+
+    _RE_BRACES = re.compile(r'^\{\s*|\s*\}$')
+    _RE_EQ = re.compile(r'([^<=>])=([^<=>])')
+    _RE_AND = re.compile(r'\band\b|,|&&|/\\|∧|∩')
+    _RE_OR = re.compile(r'\bor\b|;|\|\||\\/|∨|∪')
+    _RE_NOT = re.compile(r'\bnot\b|!|¬')
+    _RE_NUM_VAR = Expression._RE_NUM_VAR
+    _RE_OPERATORS = re.compile(r'(&|\||~)')
+
     @classmethod
     def fromstring(cls, string):
-        raise NotImplementedError
+        # remove curly brackets
+        string = cls._RE_BRACES.sub(r'', string)
+        # replace '=' by '=='
+        string = cls._RE_EQ.sub(r'\1==\2', string)
+        # replace 'and', 'or', 'not'
+        string = cls._RE_AND.sub(r' & ', string)
+        string = cls._RE_OR.sub(r' | ', string)
+        string = cls._RE_NOT.sub(r' ~', string)
+        # add implicit multiplication operators, e.g. '5x' -> '5*x'
+        string = cls._RE_NUM_VAR.sub(r'\1*\2', string)
+        # add parentheses to force precedence
+        tokens = cls._RE_OPERATORS.split(string)
+        for i, token in enumerate(tokens):
+            if i % 2 == 0:
+                token = '({})'.format(token)
+                tokens[i] = token
+        string = ''.join(tokens)
+        tree = ast.parse(string, 'eval')
+        return cls._fromast(tree)
 
     def __repr__(self):
         assert len(self.polyhedra) >= 2