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Optimize item set closure function

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This commit is contained in:
Max Brunsfeld 2014-04-26 19:06:34 -07:00
parent 93df5579b4
commit c9e0d4bdf0
1 changed files with 17 additions and 22 deletions
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39
src/compiler/build_tables/item_set_closure.cc
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@ -9,33 +9,28 @@
namespace tree_sitter {
using std::set;
using rules::ISymbol;
using std::vector;
namespace build_tables {
static bool contains(const ParseItemSet *items, const ParseItem &item) {
if (items->empty()) return false;
return (std::find(items->begin(), items->end(), item) != items->end());
}
static void add_item(ParseItemSet *item_set,
const ParseItem &item,
const PreparedGrammar &grammar) {
if (!contains(item_set, item)) {
item_set->insert(item);
for (const auto &pair : follow_sets(item, grammar)) {
const ISymbol &non_terminal = pair.first;
const set<ISymbol> &terminals = pair.second;
for (const auto &terminal : terminals) {
ParseItem next_item(non_terminal, grammar.rule(non_terminal), 0, terminal);
add_item(item_set, next_item, grammar);
}
}
}
}
const ParseItemSet item_set_closure(const ParseItem &item,
const PreparedGrammar &grammar) {
ParseItemSet result;
add_item(&result, item, grammar);
vector<ParseItem> items_to_add = { item };
while (!items_to_add.empty()) {
const ParseItem &item = items_to_add.back();
items_to_add.pop_back();
auto insertion_result = result.insert(item);
if (insertion_result.second) {
result.insert(item);
for (const auto &pair : follow_sets(item, grammar)) {
const ISymbol &non_terminal = pair.first;
const set<ISymbol> &terminals = pair.second;
for (const auto &terminal : terminals) {
items_to_add.push_back(ParseItem(non_terminal, grammar.rule(non_terminal), 0, terminal));
}
}
}
}
return result;
}
}