Add getters for if-then-else symbolic::Expression

common/symbolic_expression.cc

@@ -811,6 +811,18 @@ const string& get_uninterpreted_function_name(const Expression& e) {
   return to_uninterpreted_function(e)->get_name();
 }
 
+const Formula& get_conditional_formula(const Expression& e) {
+  return to_if_then_else(e)->get_conditional_formula();
+}
+
+const Expression& get_then_expression(const Expression& e) {
+  return to_if_then_else(e)->get_then_expression();
+}
+
+const Expression& get_else_expression(const Expression& e) {
+  return to_if_then_else(e)->get_else_expression();
+}
+
 // NOLINTNEXTLINE(runtime/references) per C++ standard signature.
 Expression& operator+=(Expression& lhs, const Variable& rhs) {
   return lhs += Expression{rhs};

common/symbolic_expression.h

@@ -626,6 +626,21 @@ get_base_to_exponent_map_in_multiplication(const Expression& e);
  */
 const std::string& get_uninterpreted_function_name(const Expression& e);
 
+/** Returns the conditional formula in the if-then-else expression @p e.
+ * @pre @p e is an if-then-else expression.
+ */
+const Formula& get_conditional_formula(const Expression& e);
+
+/** Returns the 'then' expression in the if-then-else expression @p e.
+ * @pre @p e is an if-then-else expression.
+ */
+const Expression& get_then_expression(const Expression& e);
+
+/** Returns the 'else' expression in the if-then-else expression @p e.
+ * @pre @p e is an if-then-else expression.
+ */
+const Expression& get_else_expression(const Expression& e);
+
 // Matrix<Expression> * Matrix<double> => Matrix<Expression>
 template <typename MatrixL, typename MatrixR>
 typename std::enable_if<

common/test/symbolic_expression_test.cc

@@ -43,6 +43,7 @@ using test::ExprEqual;
 using test::ExprLess;
 using test::ExprNotEqual;
 using test::ExprNotLess;
+using test::FormulaEqual;
 
 template <typename T>
 size_t get_std_hash(const T& item) {
@@ -472,6 +473,16 @@ TEST_F(SymbolicExpressionTest, GetProductsInMultiplication) {
   EXPECT_PRED2(ExprEqual, products.at(z_), y_);
 }
 
+TEST_F(SymbolicExpressionTest, GetIfThenElse) {
+  const Formula conditional{x_ > y_};
+  const Expression e1{x_ + y_};
+  const Expression e2{x_ - y_};
+  const Expression e{if_then_else(conditional, e1, e2)};
+  EXPECT_PRED2(FormulaEqual, get_conditional_formula(e), conditional);
+  EXPECT_PRED2(ExprEqual, get_then_expression(e), e1);
+  EXPECT_PRED2(ExprEqual, get_else_expression(e), e2);
+}
+
 TEST_F(SymbolicExpressionTest, IsPolynomial) {
   const vector<pair<Expression, bool>> test_vec{
       {e_constant_, true}, {e_var_, true},   {e_neg_, true},