/*
 * functions for use with programs that count alphabetic characters
 */
#ifndef ALPHABET_H /* just in case we forget and #include this twice */
#define ALPHABET_H

/* 
 * function to build "alphabet" -- all characters for which islower()
 *   is true.
 *
 * also does some simple "sanity checking" that there are not any
 *   such characters that are negative (and exits the program if so).
 *
 * parameter "alphachars" must be array of size at least SCHAR_MAX+2.
 */
void build_alphabet(char alphachars[]);

/* 
 * function to get index of character in alphabet.
 *
 * returns index of tolower(ch) in alphabet, or -1 if not found.
 */
int char_to_index(char * alphabet, char ch);

/* 
 * function to get character from alphabet.
 *
 * returns character at alphabet[index].
 */
char index_to_char(char * alphabet, int index);

#endif /* #ifndef ALPHABET_H */