Solved: 08 - Switch Statements

Added a contract precondition to apply_operation

modules/02_control_flow/include/switch_statements.hpp

@@ -7,7 +7,9 @@ namespace control_flow {
 enum class Operation { Add, Subtract, Multiply, Divide, Unknown };
 
 [[nodiscard]] auto parse_operation(char op) -> Operation;
-[[nodiscard]] auto apply_operation(Operation op, int lhs, int rhs) -> int;
+// ReSharper disable once CppConstParameterInDeclaration
+[[nodiscard]] auto apply_operation(const Operation op, const int lhs, const int rhs) -> int
+    pre(op != Operation::Unknown);
 [[nodiscard]] auto day_name(int day) -> std::string;
 
 }  // namespace control_flow

modules/02_control_flow/src/switch_statements.cpp

@@ -2,20 +2,40 @@
 
 namespace control_flow {
 
-auto parse_operation(char op) -> Operation {
-    (void)op;
-    return Operation::Unknown;
+    // enum class Operation { Add, Subtract, Multiply, Divide, Unknown };
+auto parse_operation(const char op) -> Operation {
+    switch (op) {
+        case '+': return Operation::Add;
+        case '-': return Operation::Subtract;
+        case '*': return Operation::Multiply;
+        case '/': return Operation::Divide;
+        default: return Operation::Unknown;
+    }
 }
 
-auto apply_operation(Operation op, int lhs, int rhs) -> int {
-    (void)op; (void)lhs; (void)rhs;
-    return 0;
+auto apply_operation(const Operation op, const int lhs, const int rhs) -> int
+    pre(op != Operation::Unknown)
+{
+    switch (op) {
+        case Operation::Add: return lhs + rhs;
+        case Operation::Subtract: return lhs - rhs;
+        case Operation::Multiply: return lhs * rhs;
+        case Operation::Divide: return lhs / rhs;
+        default: return -1; // Unreachable due to contract
+    }
 }
 
-auto day_name(int day) -> std::string {
-    // TODO: 1=Monday ... 7=Sunday, else "Invalid"
-    (void)day;
-    return "Invalid";
+auto day_name(const int day) -> std::string {
+    switch (day) {
+        case 1: return "Monday";
+        case 2: return "Tuesday";
+        case 3: return "Wednesday";
+        case 4: return "Thursday";
+        case 5: return "Friday";
+        case 6: return "Saturday";
+        case 7: return "Sunday";
+        default: return "Invalid";
+    }
 }
 
 }  // namespace control_flow

modules/02_control_flow/test/switch_statements_test.cpp

@@ -9,6 +9,12 @@ TEST(SwitchStatements, ParseOperation) {
 TEST(SwitchStatements, ApplyOperation) {
     EXPECT_EQ(control_flow::apply_operation(control_flow::Operation::Add, 2, 3), 5);
     EXPECT_EQ(control_flow::apply_operation(control_flow::Operation::Multiply, 4, 5), 20);
+    // Breach of contract
+    EXPECT_DEATH(
+    {
+        (void)control_flow::apply_operation(control_flow::Operation::Unknown, 2, 3);
+    },
+    "contract violation");
 }
 
 TEST(SwitchStatements, DayName) {