7 files changed, 55 insertions, 4 deletions
diff --git a/demos/CMakeLists.txt b/demos/CMakeLists.txt
index 3afb5f91..f2df325d 100644
--- a/demos/CMakeLists.txt
+++ b/demos/CMakeLists.txt
@@ -16,6 +16,8 @@ elseif(UNIX)
 	add_subdirectory(xcb)
 endif()
 
+add_subdirectory(parse)
+
 # My computer graphics practice source codes. Needs `dlib` as dependency.
 if (CRU_BUILD_GRAPHICS_EXPERIMENTS)
 	add_subdirectory(graphics_experiments)
diff --git a/demos/parse/CMakeLists.txt b/demos/parse/CMakeLists.txt
new file mode 100644
index 00000000..ceaa5c4e
--- /dev/null
+++ b/demos/parse/CMakeLists.txt
@@ -0,0 +1,2 @@
+add_executable(cru_demo_parse_eliminate_left_recursion EliminateLeftRecursion.cpp)
+target_link_libraries(cru_demo_parse_eliminate_left_recursion PRIVATE cru_parse)
diff --git a/demos/parse/EliminateLeftRecursion.cpp b/demos/parse/EliminateLeftRecursion.cpp
new file mode 100644
index 00000000..e5b97cc0
--- /dev/null
+++ b/demos/parse/EliminateLeftRecursion.cpp
@@ -0,0 +1,21 @@
+#include <iostream>
+
+#include "cru/parse/Grammar.hpp"
+
+int main() {
+  using namespace cru::parse;
+  Grammar grammar;
+
+  auto S = grammar.CreateNonterminal(u"S");
+  auto a = grammar.CreateTerminal(u"a");
+
+  grammar.CreateProduction(u"S := S a", S, {S, a});
+  grammar.CreateProduction(u"S := a", S, {a});
+  grammar.SetStartSymbol(S);
+
+  grammar.EliminateLeftRecursions();
+
+  std::cout << grammar.ProductionsToString().ToUtf8();
+
+  return 0;
+}
diff --git a/include/cru/parse/Grammar.hpp b/include/cru/parse/Grammar.hpp
index 659c4302..606fcc33 100644
--- a/include/cru/parse/Grammar.hpp
+++ b/include/cru/parse/Grammar.hpp
@@ -49,8 +49,11 @@ class Grammar : public Object {
   // Algorithm 4.21
   void LeftFactor();
 
+ public:
+  String ProductionsToString() const;
+
  private:
-  Nonterminal* start_symbol_;
+  Nonterminal* start_symbol_ = nullptr;
   std::vector<Terminal*> terminals_;
   std::vector<Nonterminal*> nonterminals_;
   std::vector<Symbol*> symbols_;
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index ba2fbce6..5059cc82 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -10,3 +10,4 @@ endif()
 
 add_subdirectory(ui)
 
+add_subdirectory(parse)
diff --git a/src/parse/CMakeLists.txt b/src/parse/CMakeLists.txt
index de096c08..5c8a6dfa 100644
--- a/src/parse/CMakeLists.txt
+++ b/src/parse/CMakeLists.txt
@@ -7,4 +7,4 @@ add_library(cru_parse SHARED
 	Token.cpp
 	TokenType.cpp
 )
-target_link_libraries(cru_parse PUBLIC cru_common)
+target_link_libraries(cru_parse PUBLIC cru_base)
diff --git a/src/parse/Grammar.cpp b/src/parse/Grammar.cpp
index 9d486c38..19095150 100644
--- a/src/parse/Grammar.cpp
+++ b/src/parse/Grammar.cpp
@@ -1,4 +1,5 @@
 #include "cru/parse/Grammar.hpp"
+#include "cru/common/String.hpp"
 #include "cru/parse/Symbol.hpp"
 
 #include <algorithm>
@@ -19,6 +20,10 @@ Grammar::~Grammar() {
   }
 }
 
+void Grammar::SetStartSymbol(Nonterminal* start_symbol) {
+  start_symbol_ = start_symbol;
+}
+
 Terminal* Grammar::CreateTerminal(String name) {
   auto terminal = new Terminal(this, std::move(name));
   terminals_.push_back(terminal);
@@ -147,8 +152,10 @@ void Grammar::EliminateLeftRecursions() {
             auto new_right = right;
             new_right.insert(new_right.cbegin(), jp->GetRight().cbegin(),
                              jp->GetRight().cend());
-            // TODO: What should this name be.
-            CreateProduction(u"", ni, std::move(new_right));
+            CreateProduction(
+                Format(u"Merge of {} and {} (Eliminate Left Recursion)",
+                       production->GetName(), jp->GetName()),
+                ni, std::move(new_right));
           }
         }
       }
@@ -278,4 +285,19 @@ void Grammar::LeftFactor() {
     }
   }
 }
+
+String Grammar::ProductionsToString() const {
+  String result;
+
+  for (const auto& production : productions_) {
+    result += production->GetName() + u" : ";
+    result += production->GetLeft()->GetName() + u" := ";
+    for (auto s : production->GetRight()) {
+      result += s->GetName() + u" ";
+    }
+    result += u"\n";
+  }
+
+  return result;
+}
 }  // namespace cru::parse