8 files changed, 86 insertions, 8 deletions
diff --git a/src/include/calculator.hpp b/src/include/calculator.hpp
index 8c5e97a..2362258 100644
--- a/src/include/calculator.hpp
+++ b/src/include/calculator.hpp
@@ -8,9 +8,11 @@
 
 class Calculator {
 private:
+  // Private attributes.
   LCD_I2C *display;
   Keypad *default_keypad;
   Tokenizer tokenizer = Tokenizer();
+  Token **tokens;
   char default_keypad_chars[4][4] = {
     {'1', '2', '3', '+'},
     {'4', '5', '6', '-'},
@@ -25,6 +27,10 @@ private:
   };
   uint keypad_col_pins[4] = {6, 7, 8, 9};
   uint keypad_row_pins[4] = {16, 17, 18, 19};
+  // End of private attributes.
+  // Private methods.
+  void processInputs();
+  // End of private methods.
 public:
   Calculator();
   ~Calculator();
diff --git a/src/include/operand.hpp b/src/include/operand.hpp
new file mode 100644
index 0000000..cc638de
--- /dev/null
+++ b/src/include/operand.hpp
@@ -0,0 +1,10 @@
+#pragma once
+#include "syntax_tree.hpp"
+
+
+class Operand: SyntaxTree {
+  int value;
+public:
+  Operand(int value);
+  float eval() const;
+};
diff --git a/src/include/parser.hpp b/src/include/parser.hpp
new file mode 100644
index 0000000..7bc7997
--- /dev/null
+++ b/src/include/parser.hpp
@@ -0,0 +1,24 @@
+/* Grammar
+ * Expression --> Term PrimeExpression
+ * PrimeExpression --> (+|-)Expression | Null
+ * Term --> Factor PrimeTerm
+ * PrimeTerm --> (*|/)Term | Null
+ * Factor --> -Expression | (Expression) | operand */
+#pragma once
+#include "tokenizer.hpp"
+#include "syntax_tree.hpp"
+
+
+class Parser {
+private:
+  // Private methods.
+  void parseExpression();
+  void parsePrimeExpression();
+  void parseTerm();
+  void parsePrimeTerm();
+  void parseFactor();
+  // End of private methods.
+public:
+  Parser();
+  const SyntaxTree *parse();
+};
diff --git a/src/include/product.hpp b/src/include/product.hpp
new file mode 100644
index 0000000..1a87f80
--- /dev/null
+++ b/src/include/product.hpp
@@ -0,0 +1,9 @@
+#pragma once
+#include "syntax_tree.hpp"
+
+
+class Product: SyntaxTree {
+public:
+  Product(SyntaxTree *left, SyntaxTree *right);
+  float eval() const;
+};
diff --git a/src/include/substraction.hpp b/src/include/substraction.hpp
new file mode 100644
index 0000000..4a5a8c7
--- /dev/null
+++ b/src/include/substraction.hpp
@@ -0,0 +1,8 @@
+#pragma once
+#include "syntax_tree.hpp"
+
+class Substraction: SyntaxTree {
+public:
+  Substraction(SyntaxTree *left, SyntaxTree *right);
+  float eval() const;
+};
diff --git a/src/include/sum.hpp b/src/include/sum.hpp
new file mode 100644
index 0000000..35d6736
--- /dev/null
+++ b/src/include/sum.hpp
@@ -0,0 +1,8 @@
+#pragma once
+#include "syntax_tree.hpp"
+
+class Sum: SyntaxTree {
+public:
+  Sum(SyntaxTree *left, SyntaxTree *right);
+  float eval() const;
+};
diff --git a/src/include/syntax_tree.hpp b/src/include/syntax_tree.hpp
new file mode 100644
index 0000000..9edf23c
--- /dev/null
+++ b/src/include/syntax_tree.hpp
@@ -0,0 +1,12 @@
+#pragma once
+#include "tokenizer.hpp"
+
+class SyntaxTree {
+protected:
+  const SyntaxTree *left {};
+  const SyntaxTree *right {};
+public:
+  SyntaxTree(SyntaxTree *left = nullptr, SyntaxTree *right = nullptr);
+  virtual ~SyntaxTree();
+  virtual float eval() const = 0;
+};
diff --git a/src/include/tokenizer.hpp b/src/include/tokenizer.hpp
index a3f9998..7d00055 100644
--- a/src/include/tokenizer.hpp
+++ b/src/include/tokenizer.hpp
@@ -1,7 +1,7 @@
 #pragma once
 #include <regex>
 #include <string>
-#include <array>
+#define TOKENS_ARRAY_LEN 16
 
 enum Type {
   operand,
@@ -11,7 +11,8 @@ enum Type {
   division,
   left_parens,
   right_parens,
-  equals
+  equals,
+  nil
 };
 
 struct Token {
@@ -22,14 +23,14 @@ struct Token {
 class Tokenizer {
 private:
   // Private attributes
-  std::array<Token *, 16> tokens;
+  Token *tokens[17];
   const std::string *to_tokenize;
   size_t current_char_index;
   short tokens_head;
   // Regexes
-  std::regex operand_regex = std::regex("^0{1}|\\d+");
-  std::regex operation_regex = std::regex("\\+|-|/|\\*");
-  std::regex parens_regex = std::regex("(|)");
+  std::regex operand_regex = std::regex("^0{1}|^\\d+");
+  std::regex operation_regex = std::regex("^\\+|^-|/|^\\*");
+  std::regex parens_regex = std::regex("^\\(|^\\)");
   // End of private attributes
   // Private methods
   void clearTokens();
@@ -42,6 +43,6 @@ private:
 public:
   Tokenizer();
   ~Tokenizer();
-  const std::array<Token *, 16> &tokenize(const std::string &operation);
-  const std::array<Token *, 16> &getTokens();
+  Token **tokenize(const std::string &operation);
+  Token **getTokens();
 };