calc_006.s.c

a little DFA compiler.

/* Generated by re2c */
#line 1 "calc_006.s.re"
/* re2c lesson 001_upn_calculator, calc_006, (c) M. Boerger 2006 - 2007 */
#line 36 "calc_006.s.re"

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define DEBUG(stmt) stmt

int  stack[4];
int  depth = 0;

int push_num(const unsigned char *t, const unsigned char *l, int radix)
{
	int num = 0;
	
	if (depth >= sizeof(stack))
	{
		return 3;
	}

	--t;
	while(++t < l)
	{
		num = num * radix + (*t - (unsigned char)'0');
	}
	DEBUG(printf("Num: %d\n", num));

	stack[depth++] = num;
	return 0;
}

int stack_add()
{
	if (depth < 2) return 4;
	
	--depth;
	stack[depth-1] = stack[depth-1] + stack[depth];
	DEBUG(printf("+\n"));
	return 0;
}

int stack_sub()
{
	if (depth < 2) return 4;

	--depth;
	stack[depth-1] = stack[depth-1] - stack[depth];
	DEBUG(printf("-\n"));
	return 0;
}

int scan(char *s)
{
	unsigned char *p = (unsigned char*)s;
	unsigned char *t;
	int res = 0;
	
#define YYCTYPE         unsigned char
#define YYCURSOR        p
	
	while(!res)
	{
		t = p;

#line 69 "<stdout>"
		{
			YYCTYPE yych;

			yych = *YYCURSOR;
			if(yych <= '*') {
				if(yych <= 0x09) {
					if(yych <= 0x00) goto yy11;
					if(yych <= 0x08) goto yy13;
				} else {
					if(yych != ' ') goto yy13;
				}
			} else {
				if(yych <= '-') {
					if(yych <= '+') goto yy7;
					if(yych <= ',') goto yy13;
					goto yy9;
				} else {
					if(yych <= '/') goto yy13;
					if(yych <= '0') goto yy4;
					if(yych <= '9') goto yy6;
					goto yy13;
				}
			}
			++YYCURSOR;
			yych = *YYCURSOR;
			goto yy21;
yy3:
#line 107 "calc_006.s.re"
			{ continue; }
#line 99 "<stdout>"
yy4:
			++YYCURSOR;
			if((yych = *YYCURSOR) <= '/') goto yy5;
			if(yych <= '9') goto yy17;
yy5:
#line 109 "calc_006.s.re"
			{ res = push_num(t, p, 10); continue; }
#line 107 "<stdout>"
yy6:
			yych = *++YYCURSOR;
			goto yy16;
yy7:
			++YYCURSOR;
#line 110 "calc_006.s.re"
			{ res = stack_add();		continue; }
#line 115 "<stdout>"
yy9:
			++YYCURSOR;
#line 111 "calc_006.s.re"
			{ res = stack_sub();		continue; }
#line 120 "<stdout>"
yy11:
			++YYCURSOR;
#line 112 "calc_006.s.re"
			{ res = depth == 1 ? 0 : 2;	break; }
#line 125 "<stdout>"
yy13:
			++YYCURSOR;
#line 113 "calc_006.s.re"
			{ res = 1; 					continue; }
#line 130 "<stdout>"
yy15:
			++YYCURSOR;
			yych = *YYCURSOR;
yy16:
			if(yych <= '/') goto yy5;
			if(yych <= '9') goto yy15;
			goto yy5;
yy17:
			++YYCURSOR;
			yych = *YYCURSOR;
			if(yych <= '/') goto yy19;
			if(yych <= '9') goto yy17;
yy19:
#line 108 "calc_006.s.re"
			{ res = push_num(t, p, 8);	continue; }
#line 146 "<stdout>"
yy20:
			++YYCURSOR;
			yych = *YYCURSOR;
yy21:
			if(yych == 0x09) goto yy20;
			if(yych == ' ') goto yy20;
			goto yy3;
		}
#line 114 "calc_006.s.re"

	}
	return res;
}

int main(int argc, char **argv)
{
	if (argc > 1)
	{
		char *inp;
		int res = 0, argp = 0, len;
		
		while(!res && ++argp < argc)
		{
			inp = strdup(argv[argp]);
			len = strlen(inp);
			if (inp[0] == '\"' && inp[len-1] == '\"')
			{
				inp[len - 1] = '\0';
				++inp;
			}
			res = scan(inp);
			free(inp);
		}
		switch(res)
		{
		case 0:
			printf("Result: %d\n", stack[0]);
			return 0;
		case 1:
			fprintf(stderr, "Illegal character in input.\n");
			return 1;
		case 2:
			fprintf(stderr, "Premature end of input.\n");
			return 2;
		case 3:
			fprintf(stderr, "Stack overflow.\n");
			return 3;
		case 4:
			fprintf(stderr, "Stack underflow.\n");
			return 4;
		}
	}
	else
	{
		fprintf(stderr, "%s <expr>\n", argv[0]);
		return 0;
	}
}