「✨」 feat(ex01): RPN is working :D

ex01/RPN.cpp

@@ -0,0 +1,55 @@
+#include "RPN.hpp"
+
+int add(int first, int second) { return first + second; }
+int subst(int first, int second) { return first - second; }
+int mult(int first, int second) { return first * second; }
+int div(int first, int second) {
+	if (second == 0)
+		throw std::invalid_argument("division by 0 is not possible");
+	return first / second;
+}
+
+
+typedef int (*OperatorFunctions)(int, int);
+
+void rpn(char *av)
+{
+	OperatorFunctions calc[128] = { NULL };
+	calc['+'] = &add;
+	calc['-'] = &subst;
+	calc['*'] = &mult;
+	calc['/'] = ÷
+
+	std::istringstream	ss_input((std::string(av)));
+	std::stack<int>		stack;
+
+	std::string value;
+
+	while (ss_input >> value)
+	{
+		if (value.size() != 1)
+			throw std::invalid_argument("invalid value");
+
+		if (isdigit(value[0]))
+		{
+			stack.push(value[0] - '0');
+			continue ;
+		}
+
+		if (!calc[(int) value[0]])
+			throw std::invalid_argument("invalid character");
+
+		if (stack.size() < 2)
+			throw std::range_error("not enough operands");
+
+		int a = stack.top(); stack.pop();
+		int b = stack.top(); stack.pop();
+		stack.push(calc[(int) value[0]](b, a));
+	}
+
+	if (stack.size() != 1)
+		throw std::range_error("there are too many operands");
+
+	std::cout << stack.top() << std::endl;
+}
+