Trying to use iddigit...

[Melchoire]

	char studentID[10];
	float iGrade = 0;
	char LetterGrade;

	cout << "Enter your 10 digit NUMERICAL student ID:\n";
	cin.getline(studentID,11);

	if (strlen(studentID) < 10) 
	{
		cout << "You student ID is too short\n";
		exit(1);
	}

	for (int i = 0; i <= 10; i++)
	{
		if (isdigit((int)studentID[i]) == false)
		{
			cout << "Your student ID is invalid\n";
			exit(1);
		}
	}

So that's my code. But the problem is even if I enter an all numeric ID, it still tells me it's invalid. What am I doing wrong?

[Duthomhas]

You've got fencepost errors. Try this:

#include <cctype>
#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;

int main()
  {

	char studentID[11];  // you need space for ten digits + one for the null char
	float iGrade = 0;
	char LetterGrade;

	cout << "Enter your 10 digit NUMERICAL student ID:\n";
	cin.getline(studentID,11);  // get max of 10 chars + one for null

	if (strlen(studentID) < 10) 
	{
		cout << "You student ID is too short\n";
		exit(1);
	}

	for (int i = 0; i < 10; i++)
	{
		if (isdigit((int)studentID[i]) == false)
		{
			cout << "Your student ID is invalid\n";
			exit(1);
		}
	}

  return 0;
  }

Good luck!

[Melchoire]

That worked great, thanks! But now I changed the first if statement a little to this:

if ((strlen(studentID) < 10) || (strlen(studentID) > 10))
	{
		cout << "You student ID is too short or too long\n";
		exit(1);//terminate the program if the id is invalid
	}

So it works fine if the ID is less than 10 digits long(it'll terminate the program) but it doesn't terminate if it's more than 10 digits. I checked it out and if you type in lets say 20 chars, it outputs 10 for the length...

[firedraco]

The cin.getline() will only get 10 characters (plus the '\0') at once, so even if they enter > 10 characters, it will only get the first 10 (I think that is how .getline() works anyway).

[Duthomhas]

http://www.cplusplus.com/reference/iostream/istream/getline/

You really should be using std::strings.

  string studentID;
  ...
  getline( cin, studentID );

  if ((studentID.length() < 10) || (studentID.length() > 20))
    ...