逆波兰计算器C++源码

#include "stack.h" #include <iostream> using namespace std; char get_command() //输入运算符 { char command; bool waiting=true; cout<<"Select command and press <Enter>:"; while(waiting) { cin>>command; command = tolower(command); //变小写 if(command=='?'||command=='='||command=='+'||command=='-'||command=='*'||command=='/'||command=='q') waiting = false; else { cout<<"Please enter a valid command:"<<endl <<"[?]push to stack [=]print top"<<endl <<"[+][-][*][/] are arithmetic operations"<<endl <<"[Q]uit."<<endl; } } return command; } bool do_command(char command,Stack &numbers) { double p,q; switch(command) { case '?': cout<<"Enter a real number:"<<flush; cin>>p; if(numbers.push(p)==overflow) cout<<"Waring:Stack full,lost number"<<endl; break; case '=': if(numbers.top(p)==underflow) cout<<"Stack empty"<<endl; else cout<<p<<endl; break; case '+': if(numbers.top(p)==underflow) cout<<"Stack empty"<<endl; else { numbers.pop(); if(numbers.top(q)==underflow) { cout<<"Stack has just one entry"<<endl; numbers.push(p); } else { numbers.pop(); if(numbers.push(q+p)==overflow) cout<<"Waring:Stack full,lost result"<<endl; } } break; case '-': if(numbers.top(p)==underflow) cout<<"Stack empty"<<endl; else { numbers.pop(); if(numbers.top(q)==underflow) { cout<<"Stack has just one entry"<<endl; numbers.push(p); } else { numbers.pop(); if(numbers.push(q-p)==overflow) cout<<"Waring:Stack full,lost result"<<endl; } } break; case '*': if(numbers.top(p)==underflow) cout<<"Stack empty"<<endl; else { numbers.pop(); if(numbers.top(q)==underflow) { cout<<"Stack has just one entry"<<endl; numbers.push(p); } else { numbers.pop(); if(numbers.push(q*p)==overflow) cout<<"Waring:Stack full,lost result"<<endl; } } break; case '/': if(numbers.top(p)==underflow) cout<<"Stack empty"<<endl; else { numbers.pop(); if(numbers.top(q)==underflow) { cout<<"Stack has just one entry"<<endl; numbers.push(p); } else { numbers.pop(); if(numbers.push(q/p)==overflow) cout<<"Waring:Stack full,lost result"<<endl; } } break; case 'q': cout<<"Calculation finished.\n"; return false; } return true; } int main() { Stack stored_numbers; while(do_command(get_command(),stored_numbers)); }