Fix Symbol == LinExpr comparisons

[linpy.git] / linpy / linexprs.py

diff --git a/linpy/linexprs.py b/linpy/linexprs.py
index ab5d344..e4ed1cc 100644 (file)
--- a/linpy/linexprs.py
+++ b/linpy/linexprs.py
@@ -178,8 +178,7 @@ class LinExpr:
         Iterate over the coefficient values in the expression, and the constant
         term.
         """
-        for coefficient in self._coefficients.values():
-            yield coefficient
+        yield from self._coefficients.values()
         yield self._constant
 
     def __bool__(self):
@@ -248,9 +247,10 @@ class LinExpr:
         """
         Test whether two linear expressions are equal.
         """
-        return isinstance(other, LinExpr) and \
-            self._coefficients == other._coefficients and \
-            self._constant == other._constant
+        if isinstance(other, LinExpr):
+            return self._coefficients == other._coefficients and \
+                self._constant == other._constant
+        return NotImplemented
 
     def __le__(self, other):
         from .polyhedra import Le
@@ -498,7 +498,9 @@ class Symbol(LinExpr):
         return True
 
     def __eq__(self, other):
-        return self.sortkey() == other.sortkey()
+        if isinstance(other, Symbol):
+            return self.sortkey() == other.sortkey()
+        return NotImplemented
 
     def asdummy(self):
         """