06/05/20 04:50:38
#include <vector>
#include <functional>
#include <stdio.h>
#include <ctype.h>
bool expression();
char buf[1000], *pc = buf;
std::vector<int> data; std::vector<bool(*)()> ops;
bool end(int c) { return c == 0 || c == '\n' || c == '\r'; }
bool get(char& c) { while (!end(*pc++)) if (!isspace(c = pc[-1])) return true; return false; }
bool get_digit(char& c) { return get(c) && (isdigit(c) || --pc && false); }
bool is(char c) { char d; return get(d) && (d == c || --pc && false); }
bool number() { char c; if (!get_digit(c)) return false; data.push_back(0); do { data.back() = 10 * data.back() + c - '0'; } while (get_digit(c)); return true; }
template<typename T> bool binary(T t) { int i = data.back(); data.pop_back(); data.back() = t(data.back(), i); return true; }
bool add() { return binary(std::plus<int>()); }
bool subtract() { return binary(std::minus<int>()); }
bool multiply() { return binary(std::multiplies<int>()); }
bool divide() { return binary(std::divides<int>()); }