When I have to reduce, saying by rule X : Y '+' X I know I have
to pop
3 times, but what happens when the rule is simply X : /* empty
*/ ? I
can't pop at all, so what should I do?
HA> Just don't pop. If s is the state on top of the state stack, the
HA> total effect is that the state goto(s, X) is pushed onto it. If
you
HA> have a stack for non-terminals and terminals, which the Bison
HA> generated parser doesn't, then X will be pushed onto that. The
rule
HA> action is executed.
$reduce: the rule we use to reduce.
$ss : the stack of state
$sl : the level of this stack. The top state is $ss[$sl-1].
$ls : the location stack, it's a stack that contains only the start
and the end line of a rule. I use it in order to have comprehensive
error message (like : syntax error between line x and y for a string,
etc).
$rule = $__xtf_parser_rule_lhs[$reduce];
/**
* We have to pop a certain amount of time
*/
$pop = $__xtf_parser_rule_count[$reduce];
$sl -= $pop;
$goto = &$__xtf_parser_goto[$__xtf_parser_sgoto[$ss[$sl-1]]];
/* call reduce handler, etc : action set by the user */
$ls[$sl-1] = array(
$ls[$sl-1][0],
$ls[$sl-2+$pop][1]
);
$ss[$sl++] = $goto[$rule];
Here I do $sl++, meaning I increment the stack level (but after). When
pop is null, should it be only $ss[$sl-1] ?