C automat

/* C program koji analizira tekst */

#include <ctype.h>
#include <stdio.h>

// tokeni
#define _EOF             0
#define _CAPITAL_WORD    1
#define _WORD            2

// pomocne funkcije
#define get_char()       getc(stdin)
#define unget_char(c)    ungetc(c, stdin)

// stanja konacnog automata
enum states{ST_START, ST_DOT, ST_CAPITAL, ST_CAPITAL_WORD, ST_SMALL, ST_WORD, ST_ERROR};

// bafer za prikupljanje znakova jedne rijeci
char word[100];

int scanner() {
    char ch;
    int state = ST_START;
    int line = 1;
    int pos = 0;
    word[0] = 0;

    while(1) {
        switch(state) {
            case ST_START : {
                ch = get_char();
                if (ch == ' ' || ch == '\t')
                    state = ST_START;
                else if (ch == '\n') {
                    line++;
                    state = ST_START;
                }
                else if (ch == '.')
                    state = ST_DOT;
                else if (isupper(ch)) {
                    word[pos++] = ch; word[pos] = 0;
                    state = ST_CAPITAL;
                }
                else if (islower(ch)) {
                    word[pos++] = ch; word[pos] = 0;
                    state = ST_SMALL;
                }
                else if (ch == EOF)
                    return _EOF;
                else state = ST_ERROR;
            }; break;

            case ST_DOT : {
                    printf("\n.\t\t\t _DOT");
                    state = ST_START;
            }; break;

            case ST_CAPITAL : {
                ch = get_char();
                if (islower(ch)) {
                    word[pos++] = ch; word[pos] = 0;
                    state = ST_CAPITAL;
                }
                else
                    state = ST_CAPITAL_WORD;
            }; break;

            case ST_CAPITAL_WORD : {
                    unget_char(ch);
                    printf("\n%-24s _CAPITAL_WORD", word);
                    word[pos = 0] = 0;
                    state = ST_START;
            }; break;

            case ST_SMALL : {
                ch = get_char();
                if (islower(ch)) {
                    state = 4;
                    word[pos++] = ch; word[pos] = 0;
                }
                else
                    state = ST_WORD;
            }; break;

            case ST_WORD : {
                    unget_char(ch);
                    printf("\n%-24s _WORD", word);
                    word[pos = 0] = 0;
                    state = ST_START;
            }; break;

            case ST_ERROR : {
                printf("\nLEXICAL ERROR on character %c in line %d", ch, line);
                state = 0;
            }; break;
        }
    }
}

int main(void) {
    scanner();
    return 0;
}