5 files changed, 53 insertions, 6 deletions
diff --git a/include/cru/parse/ParsingAlgorithm.hpp b/include/cru/parse/ParsingAlgorithm.hpp
index 1ea30a80..acca159e 100644
--- a/include/cru/parse/ParsingAlgorithm.hpp
+++ b/include/cru/parse/ParsingAlgorithm.hpp
@@ -14,7 +14,7 @@ class ParsingAlgorithm {
   CRU_DELETE_COPY(ParsingAlgorithm)
   CRU_DELETE_MOVE(ParsingAlgorithm)
 
-  ~ParsingAlgorithm() = default;
+  virtual ~ParsingAlgorithm() = default;
 
   virtual bool CanHandle(Grammar* grammar) const = 0;
   virtual ParsingAlgorithmContext* CreateContext(Grammar* grammar) const = 0;
diff --git a/include/cru/parse/ParsingAlgorithmContext.hpp b/include/cru/parse/ParsingAlgorithmContext.hpp
index 072203ec..f67ccbbc 100644
--- a/include/cru/parse/ParsingAlgorithmContext.hpp
+++ b/include/cru/parse/ParsingAlgorithmContext.hpp
@@ -1,5 +1,8 @@
 #pragma once
+#include <vector>
 #include "Grammar.hpp"
+#include "cru/parse/ParsingTreeNode.hpp"
+#include "cru/parse/Terminal.hpp"
 
 namespace cru::parse {
 class ParsingAlgorithm;
@@ -9,15 +12,17 @@ class ParsingAlgorithm;
 // contain any state machine.
 class ParsingAlgorithmContext {
  public:
-  ParsingAlgorithmContext(Grammar* grammar, ParsingAlgorithm* algorithm);
+  ParsingAlgorithmContext(Grammar* grammar, const ParsingAlgorithm* algorithm);
 
   CRU_DELETE_COPY(ParsingAlgorithmContext)
   CRU_DELETE_MOVE(ParsingAlgorithmContext)
 
-  ~ParsingAlgorithmContext();
+  virtual ~ParsingAlgorithmContext();
+
+  virtual ParsingTreeNode* Parse(const std::vector<Terminal*>& input) = 0;
 
  private:
   Grammar* grammar_;
-  ParsingAlgorithm* algorithm_;
+  const ParsingAlgorithm* algorithm_;
 };
 }  // namespace cru::parse
diff --git a/include/cru/parse/ParsingContext.hpp b/include/cru/parse/ParsingContext.hpp
index 369acf41..ebb7115a 100644
--- a/include/cru/parse/ParsingContext.hpp
+++ b/include/cru/parse/ParsingContext.hpp
@@ -1,12 +1,13 @@
 #pragma once
 #include "ParsingAlgorithmContext.hpp"
+#include "cru/parse/ParsingTreeNode.hpp"
 
 namespace cru::parse {
 // A parsing context contains all info that a program needs to know when parsing
 // a input sequence of terminals.
 class ParsingContext {
  public:
-  ParsingContext(ParsingAlgorithmContext* parsing_algorithm_context,
+  ParsingContext(const ParsingAlgorithmContext* parsing_algorithm_context,
                  std::vector<Terminal*> input);
 
   CRU_DELETE_COPY(ParsingContext)
@@ -15,7 +16,7 @@ class ParsingContext {
   ~ParsingContext();
 
  private:
-  ParsingAlgorithmContext* parsing_algorithm_context_;
+  const ParsingAlgorithmContext* parsing_algorithm_context_;
   std::vector<Terminal*> input_;
 };
 }  // namespace cru::parse
diff --git a/include/cru/parse/RecursiveDescentAlgorithm.hpp b/include/cru/parse/RecursiveDescentAlgorithm.hpp
new file mode 100644
index 00000000..c12a84f6
--- /dev/null
+++ b/include/cru/parse/RecursiveDescentAlgorithm.hpp
@@ -0,0 +1,19 @@
+#pragma once
+
+#include "ParsingAlgorithm.hpp"
+
+namespace cru::parse {
+class RecursiveDescentAlgorithm : public ParsingAlgorithm {
+ public:
+  RecursiveDescentAlgorithm() = default;
+
+  CRU_DELETE_COPY(RecursiveDescentAlgorithm)
+  CRU_DELETE_MOVE(RecursiveDescentAlgorithm)
+
+  ~RecursiveDescentAlgorithm() override = default;
+
+ public:
+  bool CanHandle(Grammar* grammar) const override;
+  ParsingAlgorithmContext* CreateContext(Grammar* grammar) const override;
+};
+}  // namespace cru::parse
diff --git a/include/cru/parse/RecursiveDescentAlgorithmContext.hpp b/include/cru/parse/RecursiveDescentAlgorithmContext.hpp
new file mode 100644
index 00000000..1b888da9
--- /dev/null
+++ b/include/cru/parse/RecursiveDescentAlgorithmContext.hpp
@@ -0,0 +1,22 @@
+#pragma once
+
+#include "ParsingAlgorithmContext.hpp"
+#include "cru/parse/ParsingTreeNode.hpp"
+#include "cru/parse/RecursiveDescentAlgorithm.hpp"
+#include "cru/parse/Terminal.hpp"
+
+namespace cru::parse {
+class RecursiveDescentAlgorithmContext : public ParsingAlgorithmContext {
+ public:
+  RecursiveDescentAlgorithmContext(Grammar* grammar,
+                                   const RecursiveDescentAlgorithm* algorithm);
+
+  CRU_DELETE_COPY(RecursiveDescentAlgorithmContext)
+  CRU_DELETE_MOVE(RecursiveDescentAlgorithmContext)
+
+  ~RecursiveDescentAlgorithmContext() override;
+
+ public:
+  ParsingTreeNode* Parse(const std::vector<Terminal*>& input) override;
+};
+}  // namespace cru::parse