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#include "cru/parse/Grammar.hpp"
#include "cru/parse/Symbol.hpp"
#include <algorithm>
#include <iterator>
#include <unordered_map>
namespace cru::parse {
Grammar::Grammar() {}
Grammar::~Grammar() {
for (auto symbol : symbols_) {
delete symbol;
}
for (auto production : productions_) {
delete production;
}
}
Terminal* Grammar::CreateTerminal(String name) {
auto terminal = new Terminal(this, std::move(name));
terminals_.push_back(terminal);
symbols_.push_back(terminal);
return terminal;
}
Nonterminal* Grammar::CreateNonterminal(String name) {
auto nonterminal = new Nonterminal(this, std::move(name));
nonterminals_.push_back(nonterminal);
symbols_.push_back(nonterminal);
return nonterminal;
}
Production* Grammar::CreateProduction(String name, Nonterminal* left,
std::vector<Symbol*> right) {
Expects(left->GetGrammar() == this);
Expects(std::all_of(right.cbegin(), right.cend(), [this](Symbol* symbol) {
return symbol->GetGrammar() == this;
}));
auto production =
new Production(this, std::move(name), left, std::move(right));
productions_.push_back(production);
return production;
}
bool Grammar::RemoveSymbol(Symbol* symbol) {
for (auto production : productions_) {
if (production->GetLeft() == symbol) return false;
for (auto s : production->GetRight()) {
if (s == symbol) return false;
}
}
auto i = std::find(symbols_.begin(), symbols_.end(), symbol);
if (i == symbols_.cend()) return false;
symbols_.erase(i);
if (auto t = dynamic_cast<Terminal*>(symbol)) {
terminals_.erase(std::find(terminals_.begin(), terminals_.end(), t));
} else if (auto n = dynamic_cast<Nonterminal*>(symbol)) {
nonterminals_.erase(
std::find(nonterminals_.begin(), nonterminals_.end(), n));
}
delete symbol;
return true;
}
bool Grammar::RemoveProduction(Production* production) {
auto i = std::find(productions_.begin(), productions_.end(), production);
if (i == productions_.cend()) return false;
productions_.erase(i);
delete production;
return true;
}
Grammar* Grammar::Clone() const {
Grammar* g = new Grammar();
std::unordered_map<Symbol*, Symbol*> symbol_map;
for (auto old_terminal : terminals_) {
auto new_terminal = g->CreateTerminal(old_terminal->GetName());
symbol_map.emplace(old_terminal, new_terminal);
}
for (auto old_nonterminal : nonterminals_) {
auto new_nonterminal = g->CreateNonterminal(old_nonterminal->GetName());
symbol_map.emplace(old_nonterminal, new_nonterminal);
}
g->SetStartSymbol(static_cast<Nonterminal*>(symbol_map[start_symbol_]));
for (auto old_production : productions_) {
std::vector<Symbol*> new_right;
std::transform(old_production->GetRight().cbegin(),
old_production->GetRight().cend(),
std::back_inserter(new_right),
[&symbol_map](Symbol* old) { return symbol_map[old]; });
g->CreateProduction(
old_production->GetName(),
static_cast<Nonterminal*>(symbol_map[old_production->GetLeft()]),
std::move(new_right));
}
return g;
}
std::unordered_map<Nonterminal*, std::vector<Production*>>
Grammar::GenerateLeftProductionMap() const {
std::unordered_map<Nonterminal*, std::vector<Production*>> result;
for (auto p : productions_) {
result[p->GetLeft()].push_back(p);
}
return result;
}
void Grammar::EliminateLeftRecursions() {
// TODO: Use a better name.
auto nonterminals = nonterminals_;
for (int i = 0; i < nonterminals.size(); i++) {
auto ni = nonterminals[i];
for (int j = 0; j < i; j++) {
auto nj = nonterminals[j];
std::vector<Production*> j_productions;
std::copy_if(
productions_.cbegin(), productions_.cend(),
std::back_inserter(j_productions),
[nj](Production* production) { return production->GetLeft() == nj; });
auto productions = productions_;
for (auto production : productions) {
if (production->GetLeft() == ni &&
production->GetRight().front() == nj) {
const std::vector<Symbol*> right(production->GetRight().cbegin() + 1,
production->GetRight().cend());
RemoveProduction(production);
for (auto jp : j_productions) {
auto new_right = right;
new_right.insert(new_right.cbegin(), jp->GetRight().cbegin(),
jp->GetRight().cend());
CreateProduction(u"", ni, std::move(new_right));
}
}
}
}
std::vector<Production*> i_r_ps;
std::vector<Production*> i_nr_ps;
for (auto p : productions_) {
if (p->GetLeft() == ni) {
if (p->GetRight().front() == ni) {
i_r_ps.push_back(p);
} else {
i_nr_ps.push_back(p);
}
}
}
auto ni_h = CreateNonterminal(u"");
for (auto p : i_nr_ps) {
auto right = p->GetRight();
right.push_back(ni_h);
CreateProduction(u"", ni, std::move(right));
}
for (auto p : i_r_ps) {
auto right = p->GetRight();
right.erase(right.cbegin());
right.push_back(ni_h);
CreateProduction(u"", ni_h, std::move(right));
}
CreateProduction(u"", ni_h, std::vector<Symbol*>{});
for (auto p : i_r_ps) {
RemoveProduction(p);
}
for (auto p : i_nr_ps) {
RemoveProduction(p);
}
}
}
} // namespace cru::parse
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