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#include <stdio.h> // printf(char *, ...)
#include <stdlib.h> // exit(int)
/*
* For grammar: (https://en.wikipedia.org/wiki/Recursive_ascent_parser)
* (R1) expr : expr _ '+' term { $$ = $1 + $3; }
* (R2) | expr _ '-' term { $$ = $1 - $3; }
* (R3) | _ term { $$ = $1; }
* ;
*
* (R4) term : _ '(' expr ')' { $$ = $2; }
* (R5) | _ num { $$ = $1; }
* ;
*
* (R6) num : _ '0' { $$ = 0; }
* (R7) | _ '1' { $$ = 1; }
* ;
*/
#pragma GCC diagnostic ignored "-Wunused-value"
#pragma GCC diagnostic ignored "-Wunused-parameter"
#define DIE(...) (printf("ERROR %s:%d\n", __FILE__, __LINE__), __VA_OPT__(exit(__VA_ARGS__),) exit(1), 1)
enum nonterminal { INVAILID, EXPR, TERM, NUM };
struct result { enum nonterminal nonterm; int value; int depth; char *s; };
struct args { int args[2]; };
#define new_arg(...) (struct args){{__VA_ARGS__}}
#define get_arg(a, n) ((a).args[n])
// top-down
struct result rule0(char *s, struct args a);
struct result rule1(char *s, struct args a);
struct result rule2(char *s, struct args a);
struct result rule3(char *s, struct args a);
struct result rule4(char *s, struct args a);
struct result rule5(char *s, struct args a);
struct result rule6(char *s, struct args a);
struct result rule7(char *s, struct args a);
// bottom-up
struct result accept(char *s, struct args a);
struct result expr(char *s, struct args a);
struct result expr2(char *s, struct args a);
struct result term(char *s, struct args a);
struct result num(char *s, struct args a);
int main(void)
{
char *s = "1-((0-1)+1+1+1+1+1)-0+1-(((1)))+1+1+1-1+0+(1-0+1)-1-0";
struct result r = accept(s, new_arg(0));
printf("%s = %d\n", s, r.value);
return 0;
}
char *eat(char *s, char c)
{
if(*s == c)
return s + 1;
else DIE();
}
struct result rule0(char *s, struct args a)
{
struct result r = {0, 0, 0, s};
r = expr(r.s, a);
r.s = eat(r.s, '\0');
return r;
}
struct result rule1(char *s, struct args a)
{
struct result r = {0, 0, 0, s};
r.s = eat(r.s, '+');
r = term(r.s, a);
return (struct result){EXPR, get_arg(a, 0) + r.value, 0, r.s};
}
struct result rule2(char *s, struct args a)
{
struct result r = {0, 0, 0, s};
r.s = eat(r.s, '-');
r = term(r.s, a);
return (struct result){EXPR, get_arg(a, 0) - r.value, 0, r.s};
}
struct result rule3(char *s, struct args a)
{
struct result r = {0, 0, 0, s};
r = term(r.s, a);
return (struct result){EXPR, r.value, 0, r.s};
}
struct result rule4(char *s, struct args a)
{
struct result r = {0, 0, 0, s};
r.s = eat(r.s, '(');
r = expr(r.s, a);
r.s = eat(r.s, ')');
return (struct result){EXPR, r.value, 1, r.s};
}
struct result rule5(char *s, struct args a)
{
struct result r = {0, 0, 0, s};
r = num(r.s, a);
return (struct result){TERM, r.value, 0, r.s};
}
struct result rule6(char *s, struct args a)
{
struct result r = {0, 0, 0, s};
r.s = eat(r.s, '0');
return (struct result){NUM, 0, 0, r.s};
}
struct result rule7(char *s, struct args a)
{
struct result r = {0, 0, 0, s};
r.s = eat(r.s, '1');
return (struct result){NUM, 1, 0, r.s};
}
struct result accept(char *s, struct args a)
{
struct result r = {0};
switch(*s) {
case '(':
case '0':
case '1': r = rule0(s, a); break;
default: DIE();
}
return r;
}
struct result expr(char *s, struct args a)
{
struct result r = {0};
switch(*s) {
case '(':
case '0':
case '1': r = rule3(s, a); break;
default: DIE();
}
struct result r2 = r;
while(r2.depth == 0) {
r = r2;
switch(r.nonterm) {
case EXPR: r2 = expr2(r.s, new_arg(r.value)); break;
default: DIE();
}
}
r.depth--;
return r;
}
struct result expr2(char *s, struct args a)
{
struct result r = {0};
switch(*s) {
case '+': r = rule1(s, a); break;
case '-': r = rule2(s, a); break;
default: r.depth = 1;
}
return r;
}
struct result term(char *s, struct args a)
{
struct result r = {0};
switch(*s) {
case '(': r = rule4(s, a); break;
case '0': r = rule5(s, a); break;
case '1': r = rule5(s, a); break;
default: DIE();
}
return r;
}
struct result num(char *s, struct args a)
{
struct result r = {0};
switch(*s) {
case '0': r = rule6(s, a); break;
case '1': r = rule7(s, a); break;
default: DIE();
}
return r;
}
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