简单计算器

#include<iostream>

#include<iomanip>

#include<string>

#include<stack>

char a[300];

int length2;

using namespace std;

stack<double> P;

stack<char> C;

int main()

{
void yunsuan();
while (gets_s(a) != NULL)
{
length2 = strlen(a);
if (a[0] == '0'&&length2 == 1) break;
yunsuan();
}
return 0;

}

void yunsuan()

{
bool panduan(char, char);
for (int i = 0; i < length2; i++)
{
if (a[i] == ' ') continue;
if (a[i] >= '0'&&a[i] <= '9')
{
double temp = 0;
while (a[i] >= '0'&&a[i] <= '9')
{
temp = 10 * temp;
temp = temp + a[i] - '0';
i++;
}
P.push(temp);
}
if (a[i] == '+' || a[i] == '-' || a[i] == '*' || a[i] == '/')
{
if (C.empty()) C.push(a[i]);
else
{
while(panduan(C.top(), a[i]))
{
double t = P.top();
P.pop();
double d = P.top();
P.pop();
if (C.top() == '*') P.push(t*d);
else if (C.top() == '+') P.push(t + d);
else if (C.top() == '-') P.push(d - t);
else P.push(d / t);
C.pop();
if (C.empty()) break;
}
C.push(a[i]);
}
}
}
double s;
while(!C.empty())
{
double x3, x4;
x3 = P.top(); P.pop();
x4 = P.top(); P.pop();
if (C.top() == '+') P.push(x3 + x4);
else if (C.top() == '*') P.push(x3*x4);
else if (C.top() == '-') P.push(x4 - x3);
else P.push(x4 / x3);
C.pop();
}
cout << setiosflags(ios::fixed) << setprecision(2) << P.top()<< endl;
P.pop();

}

bool panduan(char ch1,char ch2)

{
if (ch1 == '/' || ch1 == '*') return true;
if (ch2 == '+' || ch2 == '-') return true;
return false;

}