/**** lexer.c *********************************************/

#include "global.h"

char lexbuf[BSIZE]; int lineno = 1;
int tokenval = NONE;

int lexan( )			/* lexical analyzer */
{
    int t; 
    while (1) {
        t = getchar();
        if (t == ' ' || t == '\t')
		; 		/* strip out white space */
	else if (t == '\n')
		lineno = lineno + 1;
	else if (isdigit(t)) {	/* t is a digit */
		ungetc(t, stdin);
		scanf ( "%d", &tokenval); 
		return NUM;
	}
	else if (isalpha(t)) {		/* t is a letter */
		int p, b = 0;
		while (isalnum(t)) { 	/* t is alphanumeric */
		    lexbuf[b] = t;
		    t = getchar();
		    b = b + 1;
		    if (b >= BSIZE) error("compiler error" ); 
		}

		lexbuf[b] = EOS;
		if (t != EOF)
		    ungetc(t, stdin);
		    p = lookup(lexbuf);
		    if (p == 0)
		        p = insert(lexbuf, ID); 
		    tokenval = p;
		    return symtable[p].token;

		}
		else if (t == EOF) return DONE;

		else {
		tokenval = NONE; return t;
		}

    }
}