/*
	Little Smalltalk lexical analyzer for driver 
		timothy a. budd 12/84
*/
/*
	The source code for the Little Smalltalk System may be freely
	copied provided that the source of all files is acknowledged
	and that this condition is copied with each file.

	The Little Smalltalk System is distributed without responsibility
	for the performance of the program and without any guarantee of
	maintenance.

	All questions concerning Little Smalltalk should be addressed to:

		Professor Tim Budd
		Department of Computer Science
		The University of Arizona
		Tucson, Arizona
		85721
		USA
*/
# include <stdio.h>
# include <ctype.h>
# include <math.h>
# define DRIVECODE
# include "drive.h"

# define MAXTOKEN 100
char toktext[MAXTOKEN];
tok_type t;
int token;

extern char *lexptr;
extern double atof();

static char ocbuf = 0;
static int pbbuf[20];

# define input() (ocbuf ? pbbuf[--ocbuf] : *lexptr++ )
# define putbak(c) (pbbuf[ocbuf++] = c)

static char *psuvars[] = {"nil", "true", "false", "smalltalk", 0};
static int psuval[] = {nilvar, truevar, falsevar, smallvar};
static char symbols[] = "\n-()[]!|.;>" ;
static int symval[] = {NL, MINUS, LP, RP, LB, RB, BAR, BAR, 
	PERIOD, SEMI, PE};

static int lexsave(type)
int type;
{	char *w_search();

	if (! (t.c = w_search(toktext, 1)))
		lexerr("cannot create symbol %s", toktext);
	/* assign token, and return value */
	return(token = type);
}

int nextlex() {
	register char c;
	register char *p;
	char *q;
	int  i, n, base;
	double d, denom;

	do {			/* read whitespace (including comments) */
		c = input();
		if (c == '\"') {
			while ((c = input()) && c != '\"') ;
			if (c == '\"') c = input();
			else lexerr("unterminated comment", "");
			}
		} while (c == ' ' || c == '\t') ;

	if (!c) return(token = nothing);

	p = toktext;
	*p = c;
	toktext[1] = '\0';

						/* identifiers and keywords */
	if (( c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')) {
		for (*p++ = c; (c = input()) && isalnum(c) ; *p++ = c) ;
		*p = '\0';
		lexsave(0);
		if (c == ':') {
			return(token = KEYWORD);
			}
		else {
			putbak(c);
			if (islower(toktext[0])) {
				for (i = 0; psuvars[i]; i++)
					if (strcmp(toktext, psuvars[i]) == 0) {
						t.p = psuval[i];
						return(token = PSEUDO);
						}
				return(token = LOWERCASEVAR);
				}
			else {
				return(token = UPPERCASEVAR);
				}
			}
		}
	
# define scandigits(x) for(*p++ = c; (c = input()) && isdigit(c); *p++ = c) x

	if (c >= '0' && c <= '9') {		/* numbers */
		i = c - '0';
		scandigits( i = 10 * i + (c - '0') );
		if (c == '.' || c == 'e') {
			if (c == '.') {
				/* peek at the next char to make sure */
				n = input(); putbak(n);
				if (! isdigit(n)) goto ret_int;
				scandigits(0);
				}
			if (c == 'e') {
				*p++ = c;
				c = input();
				if (c == '+' || c == '-') {
					*p++ = c; c = input(); }
				scandigits(0);
				}
			putbak(c);
			*p = '\0';
			t.f = atof(toktext);
			return(token = LITFNUM);
			}
		else if ((c == 'r') && ((i >= 2) && (i <= 36))) {
			base = i;
			i = 0;
			for (*p++ = c; c = input(); *p++ = c) {
				if (isdigit(c)) n = c - '0';
				else if (isupper(c)) n = (c - 'A') + 10;
				else break;
				if (n >= base) break;
				i = base * i + n;
				}
			if (c == '.' || c == 'e') {
				d = (double) i;
				if (c == '.') {

					/* just peek at the next char */
					n = input(); putbak(n);
					if ((! isdigit(n)) && (! isupper(n))) 
						goto ret_int;

					denom = 1.0 / (double) base;
					for (*p++ = c; c = input(); *p++ = c) {
						if (isdigit(c))
							n = c - '0';
						else if (isupper(c))
							n = (c - 'A') + 10;
						else break;
						if (n >= base) break;
						d += n * denom;
						denom /= base;
						}
					}
				if (c == 'e') {
					*p++ = c;
					c = input();
					if (c == '+' || c == '-') {
						n = c;
						*p++ = c;
						c = input();
						}
					else n = 0;
					i = c - '0';
					scandigits(i = 10 * i + (c - '0'));
					if (n == '-') i = - i;
					d *= pow((double) base, (double) i);
					}
				putbak(c);
				*p = '\0';
				t.f = d;
				return(token = LITFNUM);
				}
			}

	ret_int:
		putbak(c);
		*p = '\0';
		t.i = i;
		return(token = LITNUM);
		}

	if (c == '#') {				/* symbol */
		i = 1;
		while (i)
			switch(c = input()) {
				case '\0': case ' ': case '\t': case '\n':
				case '(': case '[': case ')':
					putbak(c);
					i = 0;
					break;
				default:
					*p++ = c;
				}
		if (p == toktext)
			return(token = PS);
		else {
			*p = '\0';
			if ((p - toktext) >= MAXTOKEN) cant_happen(18);
			return(lexsave(LITSYM));
			}
		}

	if (c == '\'') {			/* quoted string */
		do {
			for ( ; (c = input()) && c != '\'' ; *p++ = c) ;
			c = input();
			if (c == '\'') *p++ = '\'';
			} while (c == '\'');
		putbak(c);
		*p = '\0';
		if ((p - toktext) >= MAXTOKEN) cant_happen(18);
		t.c = toktext;
		return(token = LITSTR);
		}

	if (c == ':') {				/* colon or argument name */
		c = input();
		if (c == '=') 
			return(token = ASSIGN);
		else if (isalnum(c)) {
			for (*p++ = c; isalnum(c = input()); *p++ = c );
			putbak(c);
			*p = '\0';
			return(lexsave(COLONVAR));
			}
		putbak(c);
		return(lexsave(BINARY));
		}

	if (c == '<') {			/* assign, less than or primitive */
		*p++ = c; *p = '\0';
		c = input();
		if (c == '-')
			return(token = ASSIGN);
		for (p = q = "primitive"; *p && *p == c; p++)
			c = input();
		putbak(c);
		if (*p) {
			for (p--; p >= q; p--) putbak(*p);
			return(lexsave(BINARY));
			}
		else 
			return(token = PRIMITIVE);
		}

	if (c == '.') {			/* number or period */
		c = input();
		if (c >= '0' && c <= '9') {
			putbak(c);		/* reparse with digit */
			putbak('.');		/* inserted on front */
			putbak('0');		/* so it looks like */
			return(nextlex());	/* a number */
			}
		putbak(c);
		return(token = PERIOD);
		}

	if (c == '\\') {		/* binary or hidden newline */
		c = input();
		if (c == '\n')
			return(nextlex());
		putbak(c);
		return(lexsave(BINARY));
		}

	if (c == '$') {			/* literal character or binary */
		c = input();
		if (c) {
			t.i = c;
			return(token = LITCHAR);
			}
		return(lexsave(BINARY));
		}

	for (i = 0; symbols[i]; i++)
		if (c == symbols[i])
			return(lexsave(symval[i]));

	return(lexsave(BINARY));
}