Trying to write a base converter

binarysolo (14)
I'm trying to write a base converter that allows the user to convert any number from base x to base y (2-16).

It will also allow for hexadecimal conversion. This is where I'm running into problems.

I'm trying to figure out how to discard any erroneous input (i.e. characters 'G' - 'Z' ) as they shouldn't be converted to hex since they are not within the normal hex range 'A' - 'F'.

Here is the code I've written below. 

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#include <iostream>
#include <string>
#include <cctype>
using namespace std;
 
int main()
{
        char numIn[15];
        int num[15];
        char values[17] = "0123456789ABCDEF"; // array used for table lookup
        int ob, nb, i;
   
        cout << "Enter the the number you want to convert: ";
		cin >> numIn;

        // convert string to upper case
        strupr(numIn);
 
        cout << "Enter the original base (2-16): ";
        cin >> ob;

		//bool checkValue(char numIn){
		//	if(numIn < 0 || numIn > 9){
		//	if(numIn < 'a' || numIn > 'f'){
		//	 cout << "omg error";
		//	 return false;
		//	}

		//	}
		//}

        // range checking
        while(ob < 2 || ob > 16)
        {
                cout << "Base isn't 2-16. Please re-enter: " << endl;
                cin >> ob;
        }
 
        cout << "Enter the new base (2-16): ";
        cin >> nb;
 
        // range checking
        while(nb < 2 || nb > 16)
        {
                cout << "Base isn't 2-16. Please re-enter: " << endl;
                cin >> nb;
        }


        // find the string length for the loop
        int length = strlen(numIn);
        cout << "The length of the string is: " << length << endl;
		
		
		// reverse the string for later use
		strrev (numIn); // this reverses the string
		cout << "After reversing the string, the string is: ";
		
		
		for(i = length - 1; i >= 0; i--)
		{
		  cout << numIn[i];
		}
	  
	  cout << endl; 
 
        // loop through each subscript of the input
        for(i=0; i < length; i++)
        {
 
                // check to see if it's a letter or number
                if(isdigit(numIn[i]))
                {
                num[i] = numIn[i] - 48;
                }
                else 
                {
                num[i] = numIn[i] - 55;
                }
				
				cout << num[i] << " ";
        }
 
        return 0;
}


Any help or assistance in the right direction would be greatly appreciated.
firedraco (6246)
Create a function that takes an array of chars, then goes through and makes sure everything in the array is within the correct values...here is an example to make sure everything is a number [1-5]:

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bool checkString(char* String, unsigned int size) {
    for(unsigned int i = 0; i < size; ++i) {
        if(String[i] < '1' && String[i] > '5') return false;
    }
    return true;
}
binarysolo (14)
I am so confused right now. So I'll declare this above the main program and call it when the user is prompted to enter in their numbers?
firedraco (6246)
No, I mean you should just make a function that takes the string and tells you whether or not it is valid.

If you don't know what a function is:
http://www.cplusplus.com/doc/tutorial/functions/
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