From ee0252298ab03c1647b7dcac302ac9fd4e7e8379 Mon Sep 17 00:00:00 2001
From: HombreLaser <sebastian-440@live.com>
Date: Sat, 26 Mar 2022 13:18:12 -0600
Subject: Añadido código del lexer
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---
 include/exceptions.hpp |  23 +++++++++++
 include/lexer.hpp      |  28 ++++++++-----
 lexer.cpp              | 104 ++++++++++++++++++++++++++++++++++++++++++++++---
 3 files changed, 141 insertions(+), 14 deletions(-)
 create mode 100644 include/exceptions.hpp

diff --git a/include/exceptions.hpp b/include/exceptions.hpp
new file mode 100644
index 0000000..0469784
--- /dev/null
+++ b/include/exceptions.hpp
@@ -0,0 +1,23 @@
+#include <string>
+#ifndef EXCEPTIONS_H
+#define EXCEPTIONS_H
+
+class Exception{
+private:
+  std::string error_msg;
+public:
+  Exception(const std::string &error_msg);
+  std::string showMsg();
+};
+
+class LexerException: public Exception{
+public:
+  LexerException(const std::string &error_msg): Exception(error_msg){}
+};
+
+class ParserException: public Exception{
+public:
+  ParserException(const std::string &error_msg): Exception(error_msg){}
+};
+
+#endif /* EXCEPTIONS_H */
diff --git a/include/lexer.hpp b/include/lexer.hpp
index 8d0d826..e674999 100644
--- a/include/lexer.hpp
+++ b/include/lexer.hpp
@@ -7,7 +7,14 @@
 #ifndef LEXER_H
 #define LEXER_H
 
-const std::string EMPTY_STRING = ""; 
+enum function_name{
+  sin,
+  cos,
+  tan,
+  csc,
+  sec,
+  ctg
+};
 
 enum token_type{
   sum,
@@ -17,29 +24,32 @@ enum token_type{
   power,
   variable,
   number,
-  sin,
-  cos,
-  tan,
   function,
   left_parens,
-  right_parens
+  right_parens,
+  nil
 };
 
 struct Token{
   token_type type;
   std::string value;
+  Token(token_type type, std::string value) : type(type), value(value){}
 };
 
 class Lexer{
 private:
+  char var_name;
   std::string text;
-  size_t txt_ptr;
+  size_t current_char;
   Token current_token;
-  void setCurrentToken(Token val);
+  bool matchFunction(std::string function_name);
+  std::string createNumber();
 public:
-  Lexer(std::string text);
-  void nextToken();
+  Lexer(std::string text = {});
+  void setText(std::string text);
   Token getCurrentToken();
+  Token match();
+  Token nextToken();
 };
 
 #endif /* LEXER_H */
diff --git a/lexer.cpp b/lexer.cpp
index c58ebb5..9cfb2f7 100644
--- a/lexer.cpp
+++ b/lexer.cpp
@@ -3,18 +3,112 @@
  * Luis Sebastián Martínez Vega - LCC */
 
 #include <string>
+#include <cctype>
 #include "include/lexer.hpp"
+#include "include/exceptions.hpp"
 
-Lexer::Lexer(std::string text){
-  this->text = text;
+using std::string, std::isalpha, std::isdigit;
+
+Lexer::Lexer(string text): current_token(nil, {}){
+  setText(text);
 }
 
-void Lexer::setCurrentToken(Token val){
-  current_token = val;
+void Lexer::setText(string text){
+  this->text = text;
+  // Inicializamos el lexer.
+  current_token = nextToken();
+  var_name = '\0';
 }
 
 Token Lexer::getCurrentToken(){
   return current_token;
 }
 
-void Lexer::nextToken(){}
+bool Lexer::matchFunction(string function_name){
+  string name = text.substr(current_char, 2);
+  bool matched = name == function_name;
+
+  // Si hubo una coincidencia movemos el puntero.
+  if(matched)
+    current_char += 3;
+
+  return matched;
+}
+
+string Lexer::createNumber(){
+  string number;
+
+  while(isdigit(text[current_char]) && current_char < text.length())
+  {
+    number += text[current_char];
+    ++current_char;
+  }
+
+  return number;
+}
+
+Token Lexer::match(){
+  // Probamos las funciones.
+  if(current_char + 2 < text.length())
+  {
+    if(matchFunction("sin"))
+      return Token(function, "sin");
+    else if(matchFunction("cos"))
+      return Token(function, "cos");
+    else if(matchFunction("tan"))
+      return Token(function, "tan");
+    else if(matchFunction("csc"))
+      return Token(function, "csc");
+    else if(matchFunction("sec"))
+      return Token(function, "ctg");
+  }
+  
+  if(isdigit(text[current_char]))
+    return Token(number, createNumber());
+
+  if(isalpha(text[current_char]))
+  {
+    /* Si es la primera vez que se lee un token variable o
+       si la variable leída es igual a la anteriormente leída. */
+    if(var_name == '\0' || var_name == text[current_char])
+      return Token(variable, string(1, var_name));
+
+    // Error, se introdujo una expresión con dos o más variables.
+    throw LexerException("Encontrada más de una variable.");
+  }
+
+  /* El token actual no es ni una variable, número o función.
+     Ahora a probar operadores. */
+  switch(text[current_char])
+  {
+  case '+':
+    ++current_char;
+    return Token(sum, {});
+  case '-':
+    ++current_char;
+    return Token(substraction, {});
+  case '*':
+    ++current_char;
+    return Token(multiplication, {});
+  case '/':
+    ++current_char;
+    return Token(division, {});
+  case '^':
+    ++current_char;
+    return Token(power, {});
+  case '(':
+    ++current_char;
+    return Token(left_parens, {});
+  case ')':
+    ++current_char;
+    return Token(right_parens, {});
+  default:
+    throw LexerException("Carácter inválido.");
+  }
+}
+
+Token Lexer::nextToken(){
+  current_token = match();
+  
+  return current_token;
+}
-- 
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