two operants

Zwei Operanten hintereinander ist nicht erlaubt

src/calc.cpp

@@ -2,11 +2,13 @@
 
 #include <stack>
 #include <stdexcept>
+#include <cmath>
 
 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 power(   int a, int b) { return std::pow(a, b); }
 int modulo(  int a, int b) { return a % b; }
 
 int pop_stack(auto &stack) {
@@ -30,6 +32,7 @@ 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(power,    stack); break;
     case '%': change_stack_state(modulo,   stack); break;
     case '0'...'9': stack.push(c - '0'); break;
     default: