Trac #20874: LPAbstractDictionary: Add objective_name method

This ticket completes the `LPAbstractDictionary` interface by providing
an `objective_name` accessor.

URL: https://trac.sagemath.org/20874
Reported by: mkoeppe
Ticket author(s): Aedi Wang
Reviewer(s): Andrey Novoseltsev

Author: Release Manager

src/sage/numerical/interactive_simplex_method.py

@@ -3166,6 +3166,26 @@ def objective_coefficients(self):
             (10, 5)
         """
 
+    @abstract_method
+    def objective_name(self):
+        r"""
+        Return the objective name of ``self``.
+        
+        OUTPUT:
+        
+        - a symbolic expression
+
+        EXAMPLES::
+
+            sage: A = ([1, 1], [3, 1])
+            sage: b = (1000, 1500)
+            sage: c = (10, 5)
+            sage: P = InteractiveLPProblemStandardForm(A, b, c)
+            sage: D = P.initial_dictionary()
+            sage: D.objective_name()
+            z
+        """
+
     @abstract_method
     def objective_value(self):
         r"""
@@ -3983,6 +4003,26 @@ def objective_coefficients(self):
         """
         return self._AbcvBNz[2]
 
+    def objective_name(self):
+        r"""
+        Return the objective name of ``self``.
+        
+        OUTPUT:
+        
+        - a symbolic expression
+        
+        EXAMPLES::
+
+            sage: A = ([1, 1], [3, 1])
+            sage: b = (1000, 1500)
+            sage: c = (10, 5)
+            sage: P = InteractiveLPProblemStandardForm(A, b, c)
+            sage: D = P.initial_dictionary()
+            sage: D.objective_name()
+            z
+        """
+        return self._AbcvBNz[6]
+
     def objective_value(self):
         r"""
         Return the value of the objective at the
@@ -4932,6 +4972,26 @@ def objective_coefficients(self):
         """
         return self.c_N() - self.y() * self.A_N()
 
+    def objective_name(self):
+        r"""
+        Return the objective name of ``self``.
+        
+        OUTPUT:
+        
+        - a symbolic expression
+        
+        EXAMPLES::
+
+            sage: A = ([1, 1], [3, 1])
+            sage: b = (1000, 1500)
+            sage: c = (10, 5)
+            sage: P = InteractiveLPProblemStandardForm(A, b, c)
+            sage: D = P.revised_dictionary()
+            sage: D.objective_name()
+            z
+        """
+        return self.problem().objective_name()
+
     def objective_value(self):
         r"""
         Return the value of the objective at the basic solution of ``self``.