mirror of https://github.com/ZDoom/qzdoom.git
136 lines
2.3 KiB
C++
136 lines
2.3 KiB
C++
/* re2c lesson 001_upn_calculator, calc_007, (c) M. Boerger 2006 - 2007 */
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/*!ignore:re2c
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- optimizing the generated code by using -b command line switch of re2c
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. This tells re2c to generate code that uses a decision table. The -b switch
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also contains the -s behavior. And -b also requires the input to be
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unsigned chars.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#define DEBUG(stmt) stmt
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int stack[4];
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int depth = 0;
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int push_num(const unsigned char *t, const unsigned char *l, int radix)
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{
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int num = 0;
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if (depth >= sizeof(stack))
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{
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return 3;
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}
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--t;
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while(++t < l)
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{
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num = num * radix + (*t - (unsigned char)'0');
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}
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DEBUG(printf("Num: %d\n", num));
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stack[depth++] = num;
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return 0;
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}
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int stack_add()
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{
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if (depth < 2) return 4;
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--depth;
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stack[depth-1] = stack[depth-1] + stack[depth];
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DEBUG(printf("+\n"));
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return 0;
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}
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int stack_sub()
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{
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if (depth < 2) return 4;
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--depth;
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stack[depth-1] = stack[depth-1] - stack[depth];
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DEBUG(printf("+\n"));
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return 0;
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}
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int scan(char *s)
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{
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unsigned char *p = (unsigned char*)s;
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unsigned char *t;
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int res = 0;
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#define YYCTYPE unsigned char
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#define YYCURSOR p
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while(!res)
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{
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t = p;
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/*!re2c
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re2c:indent:top = 2;
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re2c:yyfill:enable = 0;
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DIGIT = [0-9] ;
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OCT = "0" DIGIT+ ;
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INT = "0" | ( [1-9] DIGIT* ) ;
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WS = [ \t]+ ;
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WS { continue; }
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OCT { res = push_num(t, p, 8); continue; }
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INT { res = push_num(t, p, 10); continue; }
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"+" { res = stack_add(); continue; }
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"-" { res = stack_sub(); continue; }
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"\000" { res = depth == 1 ? 0 : 2; break; }
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[^] { res = 1; continue; }
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*/
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}
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return res;
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}
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int main(int argc, char **argv)
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{
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if (argc > 1)
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{
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char *inp;
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int res = 0, argp = 0, len;
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while(!res && ++argp < argc)
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{
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inp = strdup(argv[argp]);
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len = strlen(inp);
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if (inp[0] == '\"' && inp[len-1] == '\"')
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{
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inp[len - 1] = '\0';
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++inp;
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}
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res = scan(inp);
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free(inp);
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}
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switch(res)
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{
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case 0:
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printf("Result: %d\n", stack[0]);
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return 0;
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case 1:
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fprintf(stderr, "Illegal character in input.\n");
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return 1;
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case 2:
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fprintf(stderr, "Premature end of input.\n");
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return 2;
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case 3:
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fprintf(stderr, "Stack overflow.\n");
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return 3;
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case 4:
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fprintf(stderr, "Stack underflow.\n");
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return 4;
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}
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}
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else
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{
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fprintf(stderr, "%s <expr>\n", argv[0]);
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return 0;
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}
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}
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