Code #include #include #include #include #include #include using namespace std; bool isNumber(string line); void evolutePostfixExpr(string,ostream&); int operation(int , int , string); int main() { ifstream inFile; ofstream outFile; string filename; string expression; int choice; cout << "Enter the file name: "; cin >> filename; inFile.open(filename); cout << "\n1. Ouput on console." << endl; cout << "2. Ouput on file." << endl<<"Your choice: "; cin >> choice; if (choice == 2) { cout << "\nEnter the output file name: "; cin >> filename; outFile.open(filename); cout << "\nWrite to " << filename << endl; } while (!inFile.eof()) { getline(inFile, expression); if (choice == 2) evolutePostfixExpr(expression,outFile); else evolutePostfixExpr(expression, cout); } return 1; } void evolutePostfixExpr(string expr,ostream &out) { stack stk; string value,errorMsg; bool invalid = false; stringstream ss(expr); int ans = 0; int a, b; while (ss >> value) { if (isNumber(value)) stk.push(stoi(value)); else if (value == "+" || value == "-" || value == "*" || value == "/") { if (stk.empty() || stk.size() == 1) { invalid = true; errorMsg = "To many operators"; break; } a = stk.top(); stk.pop(); b = stk.top(); stk.pop(); ans = operation(a, b, value); stk.push(ans); } else { invalid = true; errorMsg = "Illegal Operation"; break; } } if (invalid) { out.width(30); out << left << expr; out << errorMsg << endl; return; } if (stk.size() > 1) { invalid = true; errorMsg = "To few operators."; } if (invalid) { out.width(30); out << left << expr; out << errorMsg << endl; return; } else { out.width(30); out << left << expr; out << errorMsg << stk.top()<= '0' && s[i] <= '9') == false) { return false; } } return true; } int operation(int a, int b, string op) { //Perform operation if (op == "+") return b + a; else if (op == "-") return b - a; else if (op == "*") return b * a; else if (op == "/") return b / a; return 0; }
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Code
#include<iostream>
#include<cmath>
#include<stack>
#include<string>
#include<fstream>
#include<sstream>
using namespace std;
bool isNumber(string line);
void evolutePostfixExpr(string,ostream&);
int operation(int , int , string);
int main()
{
ifstream inFile;
ofstream outFile;
string filename;
string expression;
int choice;
cout << "Enter the file name: ";
cin >> filename;
inFile.open(filename);
cout << "\n1. Ouput on console." << endl;
cout << "2. Ouput on file." << endl<<"Your choice: ";
cin >> choice;
if (choice == 2)
{
cout << "\nEnter the output file name: ";
cin >> filename;
outFile.open(filename);
cout << "\nWrite to " << filename << endl;
}
while (!inFile.eof())
{
getline(inFile, expression);
if (choice == 2)
evolutePostfixExpr(expression,outFile);
else
evolutePostfixExpr(expression, cout);
}
return 1;
}
void evolutePostfixExpr(string expr,ostream &out)
{
stack<int> stk;
string value,errorMsg;
bool invalid = false;
stringstream ss(expr);
int ans = 0;
int a, b;
while (ss >> value)
{
if (isNumber(value))
stk.push(stoi(value));
else if (value == "+" || value == "-" || value == "*" || value == "/")
{
if (stk.empty() || stk.size() == 1)
{
invalid = true;
errorMsg = "To many operators";
break;
}
a = stk.top();
stk.pop();
b = stk.top();
stk.pop();
ans = operation(a, b, value);
stk.push(ans);
}
else
{
invalid = true;
errorMsg = "Illegal Operation";
break;
}
}
if (invalid)
{
out.width(30); out << left << expr;
out << errorMsg << endl;
return;
}
if (stk.size() > 1)
{
invalid = true;
errorMsg = "To few operators.";
}
if (invalid)
{
out.width(30); out << left << expr;
out << errorMsg << endl;
return;
}
else
{
out.width(30); out << left << expr;
out << errorMsg << stk.top()<<endl;
}
}
bool isNumber(string s) {
if (s.size() == 0) return false;
for (int i = 0; i<s.size(); i++) {
if ((s[i] >= '0' && s[i] <= '9') == false) {
return false;
}
}
return true;
}
int operation(int a, int b, string op) {
//Perform operation
if (op == "+")
return b + a;
else if (op == "-")
return b - a;
else if (op == "*")
return b * a;
else if (op == "/")
return b / a;
return 0;
}
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