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qzdoom/tools/re2c/examples/001_upn_calculator/calc_007.b.re
2016-02-06 20:58:35 -06:00

135 lines
2.3 KiB
C++

/* re2c lesson 001_upn_calculator, calc_007, (c) M. Boerger 2006 - 2007 */
/*!ignore:re2c
- optimizing the generated code by using -b command line switch of re2c
. This tells re2c to generate code that uses a decision table. The -b switch
also contains the -s behavior. And -b also requires the input to be
unsigned chars.
*/
#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;
/*!re2c
re2c:indent:top = 2;
re2c:yyfill:enable = 0;
DIGIT = [0-9] ;
OCT = "0" DIGIT+ ;
INT = "0" | ( [1-9] DIGIT* ) ;
WS = [ \t]+ ;
WS { continue; }
OCT { res = push_num(t, p, 8); continue; }
INT { res = push_num(t, p, 10); continue; }
"+" { res = stack_add(); continue; }
"-" { res = stack_sub(); continue; }
"\000" { res = depth == 1 ? 0 : 2; break; }
[^] { res = 1; continue; }
*/
}
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;
}
}