Helper functions symbolname and symbolnames

[linpy.git] / pypol / linexprs.py

diff --git a/pypol/linexprs.py b/pypol/linexprs.py
index d8b020d..ed68493 100644 (file)
--- a/pypol/linexprs.py
+++ b/pypol/linexprs.py
@@ -9,7 +9,7 @@ from fractions import Fraction, gcd
 
 __all__ = [
     'Expression',
-    'Symbol', 'symbols',
+    'Symbol', 'symbols', 'symbolname', 'symbolnames',
     'Constant',
 ]
 
@@ -36,6 +36,7 @@ class Expression:
         '_constant',
         '_symbols',
         '_dimension',
+        '_hash',
     )
 
     def __new__(cls, coefficients=None, constant=0):
@@ -58,10 +59,7 @@ class Expression:
         self = object().__new__(cls)
         self._coefficients = {}
         for symbol, coefficient in coefficients:
-            if isinstance(symbol, Symbol):
-                symbol = symbol.name
-            elif not isinstance(symbol, str):
-                raise TypeError('symbols must be strings or Symbol instances')
+            symbol = symbolname(symbol)
             if isinstance(coefficient, Constant):
                 coefficient = coefficient.constant
             if not isinstance(coefficient, numbers.Rational):
@@ -77,13 +75,11 @@ class Expression:
         self._constant = constant
         self._symbols = tuple(self._coefficients)
         self._dimension = len(self._symbols)
+        self._hash = hash((tuple(self._coefficients.items()), self._constant))
         return self
 
     def coefficient(self, symbol):
-        if isinstance(symbol, Symbol):
-            symbol = str(symbol)
-        elif not isinstance(symbol, str):
-            raise TypeError('symbol must be a string or a Symbol instance')
+        symbol = symbolname(symbol)
         try:
             return self._coefficients[symbol]
         except KeyError:
@@ -106,6 +102,9 @@ class Expression:
     def dimension(self):
         return self._dimension
 
+    def __hash__(self):
+        return self._hash
+
     def isconstant(self):
         return False
 
@@ -220,9 +219,6 @@ class Expression:
         from .polyhedra import Gt
         return Gt(self, other)
 
-    def __hash__(self):
-        return hash((tuple(self.coefficients()), self._constant))
-
     def _toint(self):
         lcm = functools.reduce(lambda a, b: a*b // gcd(a, b),
             [value.denominator for value in self.values()])
@@ -337,31 +333,53 @@ class Expression:
 
 class Symbol(Expression):
 
-    __slots__ = Expression.__slots__ + (
+    __slots__ = (
         '_name',
+        '_hash',
     )
 
     def __new__(cls, name):
-        if isinstance(name, Symbol):
-            name = name.name
-        elif not isinstance(name, str):
-            raise TypeError('name must be a string or a Symbol instance')
-        name = name.strip()
+        name = symbolname(name)
         self = object().__new__(cls)
-        self._coefficients = {name: 1}
-        self._constant = 0
-        self._symbols = tuple(name)
         self._name = name
-        self._dimension = 1
+        self._hash = hash(self._name)
         return self
 
     @property
     def name(self):
         return self._name
 
+    def __hash__(self):
+        return self._hash
+
+    def coefficient(self, symbol):
+        symbol = symbolname(symbol)
+        if symbol == self.name:
+            return 1
+        else:
+            return 0
+
+    def coefficients(self):
+        yield self.name, 1
+
+    @property
+    def constant(self):
+        return 0
+
+    @property
+    def symbols(self):
+        return self.name,
+
+    @property
+    def dimension(self):
+        return 1
+
     def issymbol(self):
         return True
 
+    def __eq__(self, other):
+        return isinstance(other, Symbol) and self.name == other.name
+
     @classmethod
     def _fromast(cls, node):
         if isinstance(node, ast.Module) and len(node.body) == 1:
@@ -389,23 +407,61 @@ def symbols(names):
         names = names.replace(',', ' ').split()
     return (Symbol(name) for name in names)
 
+def symbolname(symbol):
+    if isinstance(symbol, str):
+        return symbol.strip()
+    elif isinstance(symbol, Symbol):
+        return symbol.name
+    else:
+        raise TypeError('symbol must be a string or a Symbol instance')
+
+def symbolnames(symbols):
+    if isinstance(symbols, str):
+        return symbols.replace(',', ' ').split()
+    return (symbolname(symbol) for symbol in symbols)
+
 
 class Constant(Expression):
 
+    __slots__ = (
+        '_constant',
+        '_hash',
+    )
+
     def __new__(cls, numerator=0, denominator=None):
         self = object().__new__(cls)
         if denominator is None and isinstance(numerator, Constant):
             self._constant = numerator.constant
         else:
             self._constant = Fraction(numerator, denominator)
-        self._coefficients = {}
-        self._symbols = ()
-        self._dimension = 0
+        self._hash = hash(self._constant)
         return self
 
+    def __hash__(self):
+        return self._hash
+
+    def coefficient(self, symbol):
+        symbol = symbolname(symbol)
+        return 0
+
+    def coefficients(self):
+        yield from []
+
+    @property
+    def symbols(self):
+        return ()
+
+    @property
+    def dimension(self):
+        return 0
+
     def isconstant(self):
         return True
 
+    @_polymorphic
+    def __eq__(self, other):
+        return isinstance(other, Constant) and self.constant == other.constant
+
     def __bool__(self):
         return self.constant != 0