houzhui_用栈实现后缀表达式计算_

#include "Stack.h" #include <iostream> int current; int flag=1; using namespace std; bool stack::isEmpty() { if (top == -1) { flag=0; return true; } else { return false; } } bool stack::push(const double pushvalue) { if (top == size) { cout << "illegal" << endl; flag=0; return false; } st[++top] = pushvalue; return true; } bool stack::pop(double& popvalue) { current=top; if (top == -1) { cout << "illegal" << endl; flag=0; return false; } popvalue = st[top--]; return true; } void calculator::run() { char instream; double number; while (cin >> instream) { if(flag==0) { break; } switch (instream) { case'+': case'-': case'*': case'/': calculate(instream); break; default: cin.putback(instream); cin >> number; data.push(number); } if (cin.get() == '\n') { break; } } double finalnumber; data.pop(finalnumber); if(current==0) { cout<<finalnumber<<endl; } if(current!=-1&&current>0) { cout<<"illegal"<<endl; flag=0; } } void calculator::calculate(char symbolvalue) { double a, b; if (get(a, b)) { switch (symbolvalue) { case'+': { data.push(a + b); break; } case'-': { data.push(a - b); break; } case'*': { data.push(a * b); break; } case'/': { if (b == 0.0) { clear(); break; } else { data.push(a / b); break; } } } } else { clear(); } } void calculator::clear() { data.~stack(); } bool calculator::get(double& a, double& b) { if (data.isEmpty()) { return false; } data.pop(b); if (data.isEmpty()) { return false; } data.pop(a); return true; }