c++ 计算器 能实现带括号的小数计算

#include <iostream> #include <string> using namespace std; /***************************************************************/ //定义一个Stack enum Error_code { success, overflow, underflow }; const maxsize=20; template <class T> class Stack { public: Stack(); bool empty() const; bool full() const; int size() const; void clear(); Error_code top(T &item) const; Error_code pop(); Error_code push(const T &item); private: int count; T entry[maxsize]; }; template <class T> Stack<T>::Stack() { count=0; } template <class T> bool Stack<T>::empty () const { return count==0; } template <class T> bool Stack<T>::full () const { return count==maxsize; } template <class T> int Stack<T>::size() const { return count; } template <class T> void Stack<T>::clear() { count=0; } template <class T> Error_code Stack<T>::top (T &item) const { if (empty()) return underflow; item= entry[count-1]; return success; } template <class T> Error_code Stack<T>::pop () { if (empty()) return underflow; count--; return success; } template <class T> Error_code Stack<T>::push (const T &item) { if (full()) return overflow; entry[count++]=item; return success; } /***************************************************************/ //进行计算的函数 void calculate(char s,Stack<double>&num) { double a,b; num.top (b); num.pop (); num.top (a); num.pop (); switch(s){ case'+':num.push (a+b);break; case'-':num.push (a-b);break; case'*':num.push (a*b);break; case'/':if(b!=0.0) num.push (a/b); else cout<<"分母不能为0"<<endl; break; } } /***************************************************************/ //判断优先级，得到结果的函数 void do_command(Stack<double>&num,Stack<char>&ch){ string sentence; string s; int i=0; double answer; string char_num=""; char sign; cout<<"请输入要计算的式子"<<endl; cin>>sentence; s=sentence; //接下来作为预读; while(1) { if(sentence[i]>='0'&&sentence[i]<='9'||sentence[i]=='.') { char_num=char_num+sentence[i]; i++; while(sentence[i]>='0'&&sentence[i]<='9'||sentence[i]=='.') {char_num=char_num+sentence[i]; i++;} //得到一个数以后进行压栈操作 num.push(atof(char_num.c_str())); } else { sign=sentence[i]; i++;//得到了一个字符以后进行压栈操作 ch.push (sign); } char_num="";//当且仅当读入了2个数字以上才能继续进行 if(num.size()==2) break; } while(sentence[i]!='\0'){ if(sentence[i]>='0'&&sentence[i]<='9'||sentence[i]=='.'){ char_num=char_num+sentence[i]; i++; while(sentence[i]>='0'&&sentence[i]<='9'||sentence[i]=='.'){ char_num=char_num+sentence[i]; i++; }//得到一个数以后进行压栈操作 num.push(atof(char_num.c_str())); } else { sign=sentence[i]; i++; switch(sign){ char c; case'+': case'-':ch.top(c); if(c!='(') {calculate(c,num);ch.pop();} if(ch.size()==0) {ch.push(sign);break;} ch.top(c); while(c=='+'||c=='-') {calculate(c,num);ch.pop(); if(ch.size()>=1) ch.top(c); else break;} ch.push (sign); break; case'*': case'/':if(ch.size()>=1)ch.top (c);else{cout<<"满了"<<endl;break;}//用来测试 if(c=='*'||c=='/') {calculate(c,num);ch.pop();} ch.push (sign); break; case'(':ch.push(sign); break; case')':ch.top(c); calculate(c,num); ch.pop(); ch.top(c); if(c=='(') {ch.pop();break;} else {while(c!='('){ calculate(c,num); ch.pop(); if(ch.size()>=1)ch.top(c);else break;} } if(c=='(') ch.pop(); break; case'=':ch.top (c); if(c!='(') { calculate(c,num); ch.pop(); while(ch.size()!=0){ ch.top(c); calculate(c,num); ch.pop(); } } break; default:cout<<"输入有误"<<endl;break; }//退出switch }//退出else char_num=""; } if(num.size()==1&&ch.size()==0){ num.top(answer); cout<<"计算成功"<<endl; cout<<s<<"的计算结果是"<<answer<<endl; } else { cout<<"输入有误，请重新输入一个正确的式子"<<endl; } } /***************************************************************/ //判断用户是否还是要继续计算的函数 bool yes_or_no(){ cout<<"还要继续么？输入y或n来进行选择"<<endl; string choice; cin>>choice; while(1){ if(choice=="Y"||choice=="y") return true; else if(choice=="N"||choice=="n") return false; else {cout<<"输入了错误的选择，请重新输入"<<endl; cin>>choice; } } } /***************************************************************/ //介绍程序 void introduction(){ cout<<"这是一个计算机程序，支持：+，-，*，/,(,)的浮点数运算"<<endl; cout<<"请不要以+，-，*，/开头，请注意括号的匹配"<<endl; cout<<"请不要输入不必要的括号"<<endl; } int main(){ introduction(); Stack<double>num_entry; Stack<char>ch_entry; do{ num_entry.clear(); num_entry.clear(); do_command(num_entry,ch_entry); }while(yes_or_no()); return 0; }