我需要创建一个对输入文件进行操作的 RPN 计算器。它使用 4 个标准算术运算符以及 pow 和 %。我不确定为什么以下程序不适用于最后 4 行输入。我得到最后 4 行的“SYNTAX ERROR”输出。有什么想法或建议吗？我正在使用的示例输入 .txt 文件是：
3 4 5.0 * -
7
4 * 8 30 +
香蕉
9 10 + 30 -
- 7 3-+ 2 -3+
900 40.65-20+
45.2 23.999%
10 战俘 2
正确的输出应该是：
-17
7
语法错误
语法错误
-11
9
879.35
21.201
100
#include<iostream>
#include<fstream>
#include<string>
#include<stack>
#include<sstream>
#include<math.h> //pow
#define SPACE(b) if (!(b)) throw "";
using namespace std;
double evalrpn(stack<string> & tkline);
int main(void){
string line;
ifstream inputfile;
string fileloc;
one:cout << "Enter the location of the input file: ";
getline(cin, fileloc);
inputfile.open(fileloc);
while (inputfile.fail())
{
cout << "The file at location " << fileloc << " failed to open." << endl;
goto one;
}
while (getline(inputfile, line)){
stack<string> tkline;
istringstream sstr(line);
string tk;
while (sstr >> tk)
tkline.push(tk);
if (!tkline.empty())
try {
auto z = evalrpn(tkline);
SPACE(tkline.empty());
cout << z << endl;
}
catch (...) { cout << "SYNTAX ERROR" << endl; }
}
cin.ignore();
return 0;
}
double evalrpn(stack<string> & tkline){
SPACE(!tkline.empty());
double x, y;
auto tk = tkline.top();
tkline.pop();
auto n = tk.size();
if (n == 1 && string("+-*/%'pow'").find(tk) != string::npos) {
y = evalrpn(tkline);
x = evalrpn(tkline);
if (tk[0] == '+') x += y;
else if (tk[0] == '-') x -= y;
else if (tk[0] == '*') x *= y;
else if (tk[0] == '/') x /= y;
else if (tk[0] == '%') x = fmod(x,y);
else pow(x, y);
}
else {
unsigned i; x = stod(tk, &i);
SPACE(i == n);
}
return x;
}