Are there identifiers for strings or numbers? - c++

Question

I recently developed a calculator, this is the code:
/*
*All 4 operations + percentage finder + Raise to power and more....
* by Ulisse
* ulissebenedennti#outlook.com
* Feel free to take some parts of this code an put them
* in yours, but do not take all the code and change/delete
* the comments to take the credit, trust me, it doesn't
* gives the satisfaction you expect.
*/
#include <iostream> //For cin and cout
#include <iomanip> //For setprecision()
#include <windows.h> //For SetconsoleTitle()
#include <stdlib.h> //For system()
#include <cmath> //For pow()
#include <cctype> //For isdigit()
using namespace std;
int main(){
reset:
system("cls"); //Screen cleaner
system("color 0f");
SetConsoleTitle("Calculator by Ulisse");//Setting window title
char op; //Start of the variables declaration
double a, b, ra;
string p, ms, d, me, e;
p = " + ";
ms = " - ";
d = " : ";
me = " x ";
e = " = "; //End of the variable declaration
cout << "Type now '?' for help page, or another character to continue." << endl;
cin >> op;
if (op == '?'){
help:
system("cls");
cout << "Write the whole operation.\nEXAMPLE: 2 ^ 3 \n OUTPUT: 2 ^ 3 = 8"<< endl;
cout << "(+) Sum between a and b\n(-) Subtraction between a and b" << endl;
cout << "(^) Raise to power\n(%)finds the a% of b\n(x or *)Multiplicate a by b" << endl;
cout << "(: or /) Divide a by b" << endl;
system("pause");
system("cls");
goto start;
}
else{
system("cls");
while(1){
start:
cout << "CALC> ";
cin >> a;
cin >> op;
cin >> b;
//The four operations
if (op == '+'){
cout << "RESULT" << endl;
cout << setprecision(999) << a << p << b << e << a + b << endl;
cout << "________________________________________________________________________________" << endl;
}
if (op == '-'){
cout << "RESULT" << endl;
cout << setprecision(999) << a << ms << b << e << a - b << endl;
cout << "________________________________________________________________________________" << endl;
}
if (op == '*' || op == 'x'){
cout << "RESULT" << endl;
cout << setprecision(999) << a << me << b << e << a * b << endl;
cout << "________________________________________________________________________________" << endl;
}
if (op == '/' || op == ':'){
cout << "RESULT" << endl;
cout << setprecision(999) << a << d << b << e << a / b << endl;
cout << "________________________________________________________________________________" << endl;
}
if (op == '%'){
cout << "RESULT" << endl;
cout << setprecision(999) << "The " << a << "% of " << b << " is " << b / 100 * a << endl;
cout << "________________________________________________________________________________" << endl;
}
if (op == '^'){
cout << "RESULT" << endl;
cout << setprecision(999) << a << " ^ " << b << " = " << pow (a, b) << endl;
cout << "________________________________________________________________________________" << endl;
}
//Some useful functions
if (op == 'c'){
system("cls");
}
if (op == '?'){
system("cls");
goto help;
}
if (op == 'r'){
goto reset;
}
if (op == 'b'){
system("color 0c");
Beep(400,500);
cout << "CLOSING, ARE YOU SURE?(y/n)";
system("color 0c");
cin >> op;
if(op == 'y'){
cout << "Closing..." << endl;
system("cls");
system("color 0f");
system("pause");
break;
}
if(op == 'n'){
goto start;
}
}
if (op == '<'){
if (a < b){
cout << "RESULT" << endl;
cout << setprecision(999) << a << " < " << b << e << " TRUE " << endl;
cout << "________________________________________________________________________________" << endl;
}
else{
cout << "RESULT" << endl;
cout << setprecision(999) << a << " < " << b << e << " FALSE " << endl;
cout << "________________________________________________________________________________" << endl;
}
}
if (op == '>'){
if (a > b){
cout << "RESULT" << endl;
cout << setprecision(999) << a << " > " << b << e << "TRUE" << endl;
cout << "________________________________________________________________________________" << endl;
}
else{
cout << "RESULT" << endl;
cout << setprecision(999) << a << " > " << b << e << "FALSE" << endl;
cout << "________________________________________________________________________________" << endl;
}
}
if (op == '='){
if (a == b){
cout << "RESULT" << endl;
cout << setprecision(999) << a << " = " << b << " is TRUE" << endl;
cout << "________________________________________________________________________________" << endl;
}
else{
cout << "RESULT" << endl;
cout << setprecision(999) << a << " = " << b << " is FALSE" << endl;
cout << "________________________________________________________________________________" << endl;
}
}
}
}
}
This is how it works:
You write a number, then an operator(like +, - plus other functions...) and it makes the operation between the two numbers you typed depending o what is the typed operato, so if you type 4 + 3 it will output 4 + 3 = 7.
Now that you understand how it works, let us go to the qyestion...
Is there an indentifier for a number or a character? When you type a sttring or a character when you cin >> (not a number variable) the application will start printing out characters that you did never inserted:
Input
I think like this(console output) will be printed out(until you dont close the process.
So i would like to prevent the applicatin for failing when you type an invalid input for the variable and making it executes another instruction, here's what i mean:
if(anumbervariable != number || anumbervariable == string){
cout << "invalid input" << endl;
}
This isn't a real working code, it's just a representation of what i mean, or i wouldn't came hre to make you waste you lives :)
Thanks in advance.

Answer 1

You can do something like follows
int getNumber(){
int x;
cin >> x;
while(cin.fail()){
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(),'\n');
cout << "invalid input"<<endl;
cin >> x;
}
return x;
}
If you want to do a character by character thing, C++ has an isalpha() function, so you can use !isalpha(). The numeric limits thing is the max buffer that can be taken before a new line. If you print it out, it's just some large number so that it can ignore that amount of input.