How to build an array with Bison / Yacc and recursive rule
With Bison, I figured out how to nest everything in one long line like this:
arg_list:
WORD arg_list { strcat( $1, "IFS" ); $$ = strcat($1, $2); } |
WORD
;
and
WORD arg_list { printf("%s, %s\n", $1, $2); }
But the problem is I will have to split $ 2 again in the second rule to parse it. Is there a way to populate an array and not just use concatenation? Am I going about this wrong?
If I need to build something like a linked list that might make sense, I'm just not sure what would be the correct way to bind to arg_list, then clear the memory.
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2 answers
If you have an array type with a push_front operation, this is trivial:
arg_list:
WORD arg_list { $$ = $2.push_front($1); }
WORD { $$ = new Array<string>($1); }
without it, more work is required. You can use a vector and add lines at the end (which will be in reverse order). Or you can use a linked list (which is easier if you are using direct C):
arg_list:
WORD arg_list { $$ = malloc(sizeof(struct list_elem));
$$->next = $2;
$$->val = $1; }
WORD { $$ = malloc(sizeof(struct list_elem));
$$->next = 0;
$$->val = $1; }
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%union {
char *char_ptr;
}
%token STRING
%type <char_ptr> STRING string
%%
...
string:
STRING /* Lexic analyzer return STRING and set yylval = yytext; */
| string STRING
{ char *str = (char*) malloc(strlen($1) + strlen($2) + 1);
strcpy(str, $1);
strcat(str, $2);
free($2);
free($1);
$$ = str;
}
;
%%
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