#include <stdio.h>
#include <stdlib.h>
#include "AlphabetLib.h"

int main(void) {

	char someLetter = 'F';
	int value = letterValue(someLetter);
	printf("Letter %c is the %d letter of the alphabet.\n", someLetter, value);

	int n = 13;
	char c = valueLetter(n, 0);
	printf("The letter that is %d in the alphabet is %c.\n", n, c);

	return 0;

}

#ifndef ALPHABETLIB_H_
#define ALPHABETLIB_H_

/**
 * Returns a value corresponding to the
 * alphabetical order of the letter.
 *	e.g. c = 3.
 * Not case sensitive.
**/
int letterValue(char letter);

/**
 * Returns the letter corresponding to the
 * alphabetical order of the value.
 *	e.g. 4 = D.
 * Returns upper case if uppercase != 0;
**/
char valueLetter(int value, int uppercase);

#endif /* ALPHABETLIB_H_ */

#include "AlphabetLib.h"

int letterValue(char letter){
	if (letter > 64 && letter < 91){
		return letter - 64;
	}

	if (letter > 96 && letter < 123){
		return letter - 96;
	}

	return -1;
}

char valueLetter(int value, int uppercase){

	if (value > 0 && value < 27){
		if (uppercase){
			return value + 64;
		} else {
			return value + 96;
		}

	}

	return '?';
}