From e6eef2bda79dcf2abde080943cb8f9808941e331 Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Sat, 11 Sep 2021 16:52:25 +0800
Subject: ...

---
 src/parse/Grammar.cpp | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

(limited to 'src/parse/Grammar.cpp')

diff --git a/src/parse/Grammar.cpp b/src/parse/Grammar.cpp
index a2dd14d4..3cf43237 100644
--- a/src/parse/Grammar.cpp
+++ b/src/parse/Grammar.cpp
@@ -2,6 +2,8 @@
 #include "cru/parse/Symbol.hpp"
 
 #include <algorithm>
+#include <iterator>
+#include <unordered_map>
 
 namespace cru::parse {
 Grammar::Grammar() {}
@@ -69,4 +71,35 @@ bool Grammar::RemoveProduction(Production* 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);
+  }
+
+  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;
+}
+
 }  // namespace cru::parse
-- 
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