Fix symbols() function

[linpy.git] / pypol / linear.py

diff --git a/pypol/linear.py b/pypol/linear.py
index bd7037b..845fac3 100644 (file)
--- a/pypol/linear.py
+++ b/pypol/linear.py
@@ -62,7 +62,7 @@ class Expression:
                 for symbol, coefficient in coefficients if coefficient != 0]
         if len(coefficients) == 0:
             return Constant(constant)
-        elif len(coefficients) == 1:
+        elif len(coefficients) == 1 and constant == 0:
             symbol, coefficient = coefficients[0]
             if coefficient == 1:
                 return Symbol(symbol)
@@ -135,7 +135,7 @@ class Expression:
         return False
 
     def __bool__(self):
-        True
+        return True
 
     def __pos__(self):
         return self
@@ -271,7 +271,7 @@ class Expression:
                 self.constant == other.constant
 
     def __hash__(self):
-        return hash((self._coefficients, self._constant))
+        return hash((tuple(sorted(self._coefficients.items())), self._constant))
 
     def _toint(self):
         lcm = functools.reduce(lambda a, b: a*b // gcd(a, b),
@@ -355,7 +355,7 @@ class Symbol(Expression):
 def symbols(names):
     if isinstance(names, str):
         names = names.replace(',', ' ').split()
-    return (symbol(name) for name in names)
+    return (Symbol(name) for name in names)
 
 
 @_polymorphic_operator