raising error from action?

[stef]

It is unclear to me if it is possible to raise an error from the action. In your example calculator it would make sense for example for division by zero or (int_min / -1).

thank you for this awesome project!

[arithy]

Sorry for the late reply.

An error state should be introduced as a part of the value type, which is specified using %value.
I show an example below. Only zero-division error is implemented here.

%prefix "calc"

%value "calc_result_t"

%header {
typedef struct calc_result_tag {
    int value;
    int error; /* 0: no error, 1 error. */
} calc_result_t;
}

%source {
#include <stdio.h>
#include <stdlib.h>

static calc_result_t calc_result_new(int value, int error) {
    calc_result_t r;
    r.value = value;
    r.error = error;
    return r;
}
}

statement <- _ e:expression _ EOL { if (e.error) printf("arithmetic error\n"); else printf("answer=%d\n", e); }
           / ( !EOL . )* EOL      { printf("syntax error\n"); }

expression <- e:term { $$ = e; }

term <- l:term _ '+' _ r:factor { $$ = calc_result_new(l.value + r.value, l.error | r.error); }
      / l:term _ '-' _ r:factor { $$ = calc_result_new(l.value - r.value, l.error | r.error); }
      / e:factor                { $$ = e; }

factor <- l:factor _ '*' _ r:unary { $$ = calc_result_new(l.value * r.value, l.error | r.error); }
        / l:factor _ '/' _ r:unary { $$ = (r.value != 0) ? calc_result_new(l.value / r.value, l.error | r.error) : calc_result_new(0, 1); }
        / e:unary                  { $$ = e; }

unary <- '+' _ e:unary { $$ = e; }
       / '-' _ e:unary { $$ = calc_result_new(-e.value, e.error); }
       / e:primary     { $$ = e; }

primary <- < [0-9]+ >               { $$ = calc_result_new(atoi($1), 0); }
         / '(' _ e:expression _ ')' { $$ = e; }

_      <- [ \t]*
EOL    <- '\n' / '\r\n' / '\r' / ';'

%%
int main() {
    calc_context_t *ctx = calc_create(NULL);
    while (calc_parse(ctx, NULL));
    calc_destroy(ctx);
    return 0;
}

[stef]

thank you very much, that answers my question and is a great example. thank you so much for taking the time to enlighten me! you can close this issue.