parser.cpp


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#include <string>
#include "include/parser.hpp"
#include "include/expressions.hpp"
#include "include/lexer.hpp"
#include "include/exceptions.hpp"

using std::string, std::stoi;

// De haber habido un error vaciaremos la pila de expresiones.
void Parser::panic() {
  for(auto ptr = tree_stack.begin(); ptr != tree_stack.end(); ++ptr)
    delete *ptr;

  throw ParserException("Sintaxis incorrecta.");
}

Expression *Parser::popStack() {
  Expression *val = tree_stack.back();
  tree_stack.pop_back();

  return val;
}

Expression *Parser::newTree(token_type type) {
  switch(type) {
  case sum:
    return new AddExpression(popStack(), popStack());
  case substraction:
    return new SubExpression(popStack(), popStack());
  case multiplication:
    return new MultiplicationExpression(popStack(), popStack());
  case division:
    return new DivisionExpression(popStack(), popStack());
  default: // Potencia.
    return new PowerExpression(popStack(), popStack());
  }
}

void Parser::setText(string text) {
  tokenizer.setText(text); // Se prepara el lexer.
  var.value = "{}";
  var.type = nil;
}

bool Parser::checkToken() {
  return tokenizer.getCurrentToken().type == nil;
}

Expression *Parser::parse(string expr) {
  setText(expr);
  parseExpr();

  /* Si no se ha consumido toda la cadena, lanzamos
     error. */
  if(tokenizer.getCurrentToken().type != nil)
    panic();

  return popStack();
}

void Parser::parseExpr() {
  parseTerm();
  parsePrimeExpr();
}

void Parser::parsePrimeExpr() {
  token_type current;
  
  if(tokenizer.getCurrentToken().type == sum
     || tokenizer.getCurrentToken().type == substraction) {
    current = tokenizer.getCurrentToken().type;
    tokenizer.nextToken();

    if(checkToken())
      panic();

    parseTerm();
    tree_stack.push_back(newTree(current));
    parsePrimeExpr();
  }
}

void Parser::parseTerm() {
  parsePower();
  parsePrimeTerm();
}

void Parser::parsePrimeTerm() {
  token_type current;
  
  if(tokenizer.getCurrentToken().type == multiplication
     || tokenizer.getCurrentToken().type == division) {
    current = tokenizer.getCurrentToken().type;
    tokenizer.nextToken();

    if(checkToken())
      panic();

    parsePower();
    tree_stack.push_back(newTree(current));
    parsePrimeTerm();
  }
}

void Parser::parsePower() {
  parseFactor();
  parsePrimePower();
}

void Parser::parsePrimePower() {
  if(tokenizer.getCurrentToken().type == power) {
    tokenizer.nextToken();

    if(tokenizer.getCurrentToken().type != number)
      panic();

    tree_stack.push_back(new Literal(stoi(tokenizer.getCurrentToken().value)));
    tokenizer.nextToken();

    tree_stack.push_back(newTree(power));
    parsePrimePower();
  }
}

void Parser::parseFactor() {
  trig_functions name;
  
  switch(tokenizer.getCurrentToken().type) {
  case substraction:
    tokenizer.nextToken();
    
    parseExpr();
    tree_stack.push_back(new NegationExpression(popStack()));
    
    break;
  case left_parens:
    tokenizer.nextToken();
    parseExpr();

    // Consumimos paréntesis derecho.
    if(tokenizer.getCurrentToken().type != right_parens)
      panic();

    tokenizer.nextToken();
    
    break;
  case function:    
    if(tokenizer.getCurrentToken().value == "sin")
      name = i_sin;
    else if(tokenizer.getCurrentToken().value == "cos")
      name = i_cos;
    else if(tokenizer.getCurrentToken().value == "tan")
      name = i_tan;
    else if(tokenizer.getCurrentToken().value == "csc")
      name = i_csc;
    else if(tokenizer.getCurrentToken().value == "sec")
      name = i_sec;
    else
      name = i_ctg;
    
    tokenizer.nextToken();

    if(tokenizer.getCurrentToken().type != left_parens)
      panic();

    tokenizer.nextToken();
    parseExpr();
    
    if(tokenizer.getCurrentToken().type != right_parens)
      panic();
    
    tokenizer.nextToken();
    tree_stack.push_back(new Function(popStack(), name));
    
    break;
  case variable:
    /* Checamos si no se ha registrado ningún nombre de variable o si
       la variable leída por el lexer es la misma que la que se había leído. */
    if(tokenizer.getCurrentToken().value == var.value || var.type == nil)
      var = tokenizer.getCurrentToken();
    else
      panic(); // Se introdujeron dos variables en la expresión.
    
    tree_stack.push_back(new Variable(tokenizer.getCurrentToken().value[0]));
    tokenizer.nextToken();
  
    break;
  case number:
    tree_stack.push_back(new Literal(stoi(tokenizer.getCurrentToken().value)));
    tokenizer.nextToken();

    break;
  default:
    panic();
    
    break;
  }
}