validating different input types

[binaary]

Currently writing a switch menu system and I'm looking into validating each input that the user enters against its datatype:

char, string, int, double, float. I've managed to get the int one working but it also allows double and float numbers to be entered. I'm currently trying to get the char one working but I'm having some problems, it works if I enter anything apart from a value between 65 and 121 it obiously accepts that input.

Any help or directions on where to find what I need would be greatly appriciated.


current code:

  	system ("CLS");
	int value;
    cout << "Enter Your choice:"<< endl;
    cout << "1. Integer"<<endl;
    cout << "2. Float"<<endl;
    cout << "3. Double"<<endl;
    cout << "4. Char"<<endl;
    cout << "5. String"<<endl;
    cin >> value;
    
    switch (value)
    {
        case 1:

		//Prompt the user to enter an integer.
		cout << "Enter an integer: ";
		cin >>inputIntOne;

		//While the input entered is not an integer, prompt the user to enter an integer.
		while (!(cin >> inputIntOne))
			{
				// Explain error
			    cout << "ERROR: a number must be entered:";
			    cin.clear();
			    cin.ignore(132, '\n');
			}
		break;
		insertMenu2();



    case 4:
            cout << "Enter a char";
            cin >> inputCharOne;
            while (inputCharOne <65 ||inputCharOne > 122)
				{
					// Explain error
				    cout << "ERROR: a Character must be entered:";
				    cin.clear();
				    cin.ignore(132, '\n');
				}
            break;

[Ganado]

It gets a bit hairy, depending on how "correct" you want to be.*

But for just basic parsing, you need to receive user input as the "lowest common denominator" of types you want to parse. So in this case, you would need to have the user enter a string, and then you parse that string to see if it matches the criteria of being a floating-point number, then an integer.

* What I mean by this, is there are actually a bunch of valid number literals in C++, and if you want to support all of them, it will take a bit of effort. See
https://en.cppreference.com/w/cpp/language/floating_literal
https://en.cppreference.com/w/cpp/language/integer_literal
for more details.

Edit: Well, apparently there is an easy way to do it thanks to JLBorges (excluding hexidecimal).

[JLBorges]

#include <iostream>
#include <string>
#include <cctype>

template < typename TYPE > TYPE get_val( const char* type_str )
{
    std::cout << "enter an input of type " << type_str << " and press ENTER: " ;

    TYPE value ;
    // return valid input of the correct type, immediately followed by a new line
    if( std::cin >> value && std::cin.get() == '\n' ) return value ;

    // return not executed; input error
    std::cout << "invalid input. try again\n" ;
    std::cin.clear() ;
    std::cin.ignore( 1000, '\n' ) ;
    return get_val<TYPE>(type_str) ;
}

// a preprocessor macro to provide a bit of syntactic sugar
// it simply stringifies the name of the type and forwards to our function
#define GET_VAL(type) get_val<type>( #type )

char get_alpha()
{
    std::cout << "enter an alpha charecter: " ;

    char c ;
    // return the char entered if it is an alpha character
    if( std::cin >> c && std::isalpha(c) ) return c ;

    // return not executed; input error
    std::cout << "invalid input. try again\n" ;
    return get_alpha() ;
}

int main()
{
    const int i = GET_VAL(int) ;
    std::cout << i << '\n' ;

    const double d = GET_VAL(double) ;
    std::cout << d << '\n' ;

    const std::string str = GET_VAL(std::string) ;
    std::cout << str << '\n' ;

    const char a = get_alpha() ;
    std::cout << a << '\n' ;
}

[againtry]

infatuating