Make Expression.subs() always return a LinExpr instance

[linpy.git] / linpy / linexprs.py

diff --git a/linpy/linexprs.py b/linpy/linexprs.py
index 3c00f224c87a77ae25c5d7995986d577805c4ea4..f3612185455a4afac95278af032cdaf481cc0d06 100644 (file)
--- a/linpy/linexprs.py
+++ b/linpy/linexprs.py
@@ -306,7 +306,7 @@ class LinExpr:
         for symbol in substitutions:
             if not isinstance(symbol, Symbol):
                 raise TypeError('symbols must be Symbol instances')
         for symbol in substitutions:
             if not isinstance(symbol, Symbol):
                 raise TypeError('symbols must be Symbol instances')

-        result = self._constant
+        result = Rational(self._constant)

         for symbol, coefficient in self._coefficients.items():
             expression = substitutions.get(symbol, symbol)
             result += coefficient * expression
         for symbol, coefficient in self._coefficients.items():
             expression = substitutions.get(symbol, symbol)
             result += coefficient * expression