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#include "bnf.h"
std::unordered_map<std::string, std::unordered_set<std::string>> Reverse(const BNF& bnf)
{
std::unordered_map<std::string, std::unordered_set<std::string>> result;
for (const auto& [from, to] : bnf) {
for (const auto& list : to) {
for (const auto& element : list) {
auto i{result.find(element)};
if (i != result.end()) // already present
i->second.insert(from);
else // new element
result.emplace(element, std::unordered_set{from});
}
}
}
return result;
}
std::unordered_map<std::string, std::unordered_set<std::string>> reverseFirst(const BNF& bnf)
{
std::unordered_map<std::string, std::unordered_set<std::string>> result;
for (const auto& [from, to] : bnf) {
for (const auto& list : to) {
if (list.size() > 0) {
const auto& element{list[0]};
auto i{result.find(element)};
if (i != result.end()) // already present
i->second.insert(from);
else // new element
result.emplace(element, std::unordered_set{from});
}
}
}
return result;
}
BNF SubBNF(const BNF& bnf, const std::string& top)
{
BNF result;
std::vector<std::string> todo{top};
while (!todo.empty()) {
std::string current{todo.back()};
todo.pop_back();
auto it = bnf.find(current);
if (it != bnf.end()) {
// add current value
result[it->first] = it->second;
// add sub-tree values if not present yet, but available in original bnf
for (auto& variant: it->second) {
for (auto& child: variant) {
if (result.find(child) == result.end() && bnf.find(child) != bnf.end()) {
todo.push_back(child);
}
}
}
}
}
return result;
}
namespace {
bool isHeadRecursive(const std::vector<std::string>& list, const std::string& symbol) {
if (list.size() > 0 && list[0] == symbol)
return true;
return false;
}
bool isHeadRecursive(const std::vector<std::vector<std::string>>& lists, const std::string& symbol) {
for (const auto& list: lists) {
if (isHeadRecursive(list, symbol))
return true;
}
return false;
}
} // anonymous namespace
// Change head recursion to tail recursion
BNF removeHeadRecursion(const BNF& bnf)
{
std::unordered_map<std::string, std::vector<std::vector<std::string>>> result;
for (const auto& [from, to]: bnf) {
if (isHeadRecursive(to, from)) { // modify rule by adding additional one
std::string from_ext = from + "-ext";
if (bnf.find(from_ext) != bnf.end())
throw std::runtime_error("ICE: Symbol "s + from_ext + " already exists in original BNF");
std::vector<std::vector<std::string>> to_new;
std::vector<std::vector<std::string>> to_ext{{}}; // starts with empty list as first element
for (const auto& list: to) {
if (isHeadRecursive(list, from)) {
std::vector<std::string> list_new{list.begin() + 1, list.end()};
list_new.push_back(from_ext);
to_ext.push_back(list_new);
} else {
std::vector<std::string> list_new{list.begin(), list.end()};
list_new.push_back(from_ext);
to_new.push_back(list_new);
}
}
result[from] = to_new;
result[from_ext] = to_ext;
} else { // just add
result[from] = to;
}
}
return result;
}
bool isTerminal(const BNF& bnf, const std::string& symbol)
{
return bnf.find(symbol) == bnf.end();
}
std::unordered_set<std::string> getTerminals(const BNF& bnf)
{
std::unordered_set<std::string> result;
for (const auto& [from, to] : bnf) {
for (const auto& list : to) {
for (const auto& element : list) {
if (isTerminal(bnf, element))
result.insert(element);
}
}
}
return result;
}
std::unordered_set<std::pair<std::string, size_t>, PairHash> getEmptyPositions(const BNF& bnf)
{
std::unordered_set<std::pair<std::string, size_t>, PairHash> result;
for (const auto& [from, to] : bnf) {
for (size_t i = 0; i < to.size(); i++) {
const auto& list{to[i]};
if (list.size() == 0)
result.insert({from, i});
}
}
return result;
}
std::unordered_map<std::string, std::unordered_set<std::pair<std::string, index_t>, PairHash>> reversePosFirst(const BNF& bnf)
{
std::unordered_map<std::string, std::unordered_set<std::pair<std::string, index_t>, PairHash>> result;
for (const auto& [from, to] : bnf) {
for (size_t i = 0; i < to.size(); i++) {
const auto& list{to[i]};
if (list.size() > 0) {
const auto& element{list[0]};
auto it{result.find(element)};
if (it != result.end()) // already present
it->second.insert({from, i});
else // new element
result.emplace(element, std::unordered_set<std::pair<std::string, index_t>, PairHash>{{from, i}});
}
}
}
return result;
}
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