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Fix transitions for sequences whose left side can be blank

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This commit is contained in:
Max Brunsfeld 2014-01-23 23:56:37 -08:00
parent 5776846227
commit 8208aae060
6 changed files with 98 additions and 34 deletions
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47
src/compiler/build_tables/rule_transitions.cpp
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@ -13,10 +13,6 @@ namespace tree_sitter {
public:
transition_map<Rule, Rule> value;
void visit(const Blank *rule) {
value = transition_map<Rule, Rule>({{ blank(), blank() }});
}
void visit(const Character *rule) {
value = transition_map<Rule, Rule>({{ rule->copy(), blank() }});
}
@ -39,6 +35,11 @@ namespace tree_sitter {
else
return seq({ left_rule, rule->right });
});
if (rule_can_be_blank(rule->left)) {
value.merge(rule_transitions(rule->right), [&](rule_ptr left, rule_ptr right) -> rule_ptr {
return choice({ left, right });
});
}
}
void visit(const Repeat *rule) {
@ -59,17 +60,41 @@ namespace tree_sitter {
}
};
bool rule_can_be_blank(const rule_ptr &rule) {
for (auto pair : rule_transitions(rule))
if (is_blank(pair.first))
return true;
return false;
}
transition_map<Rule, Rule> rule_transitions(const rule_ptr &rule) {
TransitionsVisitor visitor;
rule->accept(visitor);
return visitor.value;
}
class EpsilonVisitor : public rules::Visitor {
public:
bool value;
void default_visit(const Rule *) {
value = false;
}
void visit(const Blank *) {
value = true;
}
void visit(const Choice *rule) {
value = rule_can_be_blank(rule->left) || rule_can_be_blank(rule->right);
}
void visit(const Seq *rule) {
value = rule_can_be_blank(rule->left) && rule_can_be_blank(rule->right);
}
void visit(const Repeat *rule) {
value = rule_can_be_blank(rule->content);
}
};
bool rule_can_be_blank(const rule_ptr &rule) {
EpsilonVisitor visitor;
rule->accept(visitor);
return visitor.value;
}
}
}