merge

src/calc.cpp

@@ -7,6 +7,7 @@ int plus(    int a, int b) { return a + b; }
 int minus(   int a, int b) { return a - b; }
 int multiply(int a, int b) { return a * b; }
 int divide(  int a, int b) { return a / b; }
+int modulo(  int a, int b) { return a % b; }
 
 int pop_stack(auto &stack) {
   const auto ret{stack.top()};
@@ -29,6 +30,7 @@ int evaluate(const std::string &s) {
     case '-': change_stack_state(minus,    stack); break;
     case '*': change_stack_state(multiply, stack); break;
     case '/': change_stack_state(divide,   stack); break;
+    case '%': change_stack_state(modulo,   stack); break;
     case '0'...'9': stack.push(c - '0'); break;
     }
   }

test/test.cpp

@@ -27,4 +27,8 @@ TEST_CASE( "basic division", "[calc]"){
   REQUIRE( evaluate("93/") == 3);
 }
 
-
+TEST_CASE( "Test modulo function", "[calc]") {
+  REQUIRE( evaluate("11%") == 0 );
+  REQUIRE( evaluate("32%") == 1 );
+  REQUIRE( evaluate("51%") == 4 );
+}