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#include <stdio.h>
#include <stdlib.h>
/*
* For grammar: (https://en.wikipedia.org/wiki/Recursive_ascent_parser)
* expr : expr '+' term { $$ = $1 + $3; }
* | expr '-' term { $$ = $1 - $3; }
* | term { $$ = $1; }
* ;
*
* term : '(' expr ')' { $$ = $2; }
* | num { $$ = $1; }
* ;
*
* num : '0' { $$ = 0; }
* | '1' { $$ = 1; }
* ;
*/
#pragma GCC diagnostic ignored "-Wunused-value"
#define DIE(...) (printf("ERROR %s:%d\n", __FILE__, __LINE__), __VA_OPT__(exit(__VA_ARGS__),) exit(1), 1)
enum nonterminal { 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])
struct result state0(char *s, struct args a);
struct result state1(char *s, struct args a);
struct result state2(char *s, struct args a);
struct result state3(char *s, struct args a);
struct result state4(char *s, struct args a);
struct result state5(char *s, struct args a);
struct result state6(char *s, struct args a);
struct result state7(char *s, struct args a);
struct result state8(char *s, struct args a);
struct result state9(char *s, struct args a);
struct result state10(char *s, struct args a);
struct result state11(char *s, struct args a);
struct result state12(char *s, struct args a);
struct result state13(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 = state0(s, new_arg(0));
printf("%s = %d\n", s, r.value);
return 0;
}
/*
* 0 $accept: . expr $end
*
* '(' shift, and go to state 1
* '0' shift, and go to state 2
* '1' shift, and go to state 3
*
* expr go to state 4
* term go to state 5
* num go to state 6
*/
struct result state0(char *s, struct args a)
{
struct result r = {0};
switch(*s) {
case '(': r = state1(s+1, a); break;
case '0': r = state2(s+1, a); break;
case '1': r = state3(s+1, a); break;
default: DIE();
}
while(r.depth == 0) {
switch(r.nonterm) {
case EXPR: r = state4(r.s, new_arg(r.value)); break;
case TERM: r = state5(r.s, new_arg(r.value)); break;
case NUM: r = state6(r.s, new_arg(r.value)); break;
default: DIE();
}
}
r.depth--;
return r;
}
/*
* 4 term: '(' . expr ')'
*
* '(' shift, and go to state 1
* '0' shift, and go to state 2
* '1' shift, and go to state 3
*
* expr go to state 7
* term go to state 5
* num go to state 6
*/
struct result state1(char *s, struct args a)
{
struct result r = {0};
switch(*s) {
case '(': r = state1(s+1, a); break;
case '0': r = state2(s+1, a); break;
case '1': r = state3(s+1, a); break;
default: DIE();
}
while(r.depth == 0) {
switch(r.nonterm) {
case EXPR: r = state7(r.s, new_arg(r.value)); break;
case TERM: r = state5(r.s, new_arg(r.value)); break;
case NUM: r = state6(r.s, new_arg(r.value)); break;
default: DIE();
}
}
r.depth--;
return r;
}
/*
* 6 num: '0' .
*
* $default reduce using rule 6 (num)
*/
struct result state2(char *s, struct args a)
{
(void)a;
return (struct result){NUM, 0, 0, s};
}
/*
* 7 num: '1' .
*
* $default reduce using rule 7 (num)
*/
struct result state3(char *s, struct args a)
{
(void)a;
return (struct result){NUM, 1, 0, s};
}
/*
* 0 $accept: expr . $end
* 1 expr: expr . '+' term
* 2 | expr . '-' term
*
* $end shift, and go to state 8
* '+' shift, and go to state 9
* '-' shift, and go to state 10
*/
struct result state4(char *s, struct args a)
{
struct result r = {0};
switch(*s) {
case '\0': r = state8(s+1, a); break;
case '+': r = state9(s+1, a); break;
case '-': r = state10(s+1, a); break;
default: DIE();
}
(r.depth == 0) && DIE();
r.depth--;
return r;
}
/*
* 3 expr: term .
*
* $default reduce using rule 3 (expr)
*/
struct result state5(char *s, struct args a)
{
return (struct result){EXPR, get_arg(a, 0), 0, s};
}
/*
* 5 term: num .
*
* $default reduce using rule 5 (term)
*/
struct result state6(char *s, struct args a)
{
return (struct result){TERM, get_arg(a, 0), 0, s};
}
/*
* 1 expr: expr . '+' term
* 2 | expr . '-' term
* 4 term: '(' expr . ')'
*
* '+' shift, and go to state 9
* '-' shift, and go to state 10
* ')' shift, and go to state 11
*/
struct result state7(char *s, struct args a)
{
struct result r = {0};
switch(*s) {
case '+': r = state9(s+1, a); break;
case '-': r = state10(s+1, a); break;
case ')': r = state11(s+1, a); break;
default: DIE();
}
(r.depth == 0) && DIE();
r.depth--;
return r;
}
/*
* 0 $accept: expr $end .
*
* $default accept
*/
struct result state8(char *s, struct args a)
{
return (struct result){EXPR, a.args[0], 2, s};
}
/*
* 1 expr: expr '+' . term
*
* '(' shift, and go to state 1
* '0' shift, and go to state 2
* '1' shift, and go to state 3
*
* term go to state 12
* num go to state 6
*/
struct result state9(char *s, struct args a)
{
struct result r = {0};
switch(*s) {
case '(': r = state1(s+1, a); break;
case '0': r = state2(s+1, a); break;
case '1': r = state3(s+1, a); break;
default: DIE();
}
while(r.depth == 0) {
switch(r.nonterm) {
case TERM: r = state12(r.s, new_arg(r.value, get_arg(a, 0))); break;
case NUM: r = state6(r.s, new_arg(r.value)); break;
default: DIE();
}
}
r.depth--;
return r;
}
/*
* 2 expr: expr '-' . term
*
* '(' shift, and go to state 1
* '0' shift, and go to state 2
* '1' shift, and go to state 3
*
* term go to state 13
* num go to state 6
*/
struct result state10(char *s, struct args a)
{
struct result r = {0};
switch(*s) {
case '(': r = state1(s+1, a); break;
case '0': r = state2(s+1, a); break;
case '1': r = state3(s+1, a); break;
default: DIE();
}
while(r.depth == 0) {
switch(r.nonterm) {
case TERM: r = state13(r.s, new_arg(get_arg(a, 0), r.value)); break;
case NUM: r = state6(r.s, new_arg(r.value)); break;
default: DIE();
}
}
r.depth--;
return r;
}
/*
* 4 term: '(' expr ')' .
*
* $default reduce using rule 4 (term)
*/
struct result state11(char *s, struct args a)
{
return (struct result){TERM, get_arg(a, 0), 2, s};
}
/*
* 1 expr: expr '+' term .
*
* $default reduce using rule 1 (expr)
*/
struct result state12(char *s, struct args a)
{
return (struct result){EXPR, get_arg(a, 0) + get_arg(a, 1), 2, s};
}
/*
* 2 expr: expr '-' term .
*
* $default reduce using rule 2 (expr)
*/
struct result state13(char *s, struct args a)
{
return (struct result){EXPR, get_arg(a, 0) - get_arg(a, 1), 2, s};
}
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