Hi to all, I've centos6.4 in VM AND Qt5.2.1 I am building a project given in book "C++-GUI-Programming-with-Qt-4-1st-ed.pdf". but in book it is by coding and i am building by using GUI.
here is my cell.h file :-
Qt Code: 
  1. #ifndef CELL_H
  2.     #define CELL_H
  3.  
  4.     #include <QTableWidgetItem>     
  5.     #include <QWidget>
  6.  
  7.     class Cell : public QTableWidgetItem
  8.     {
  9.  
  10.     public:
  11.         Cell();
  12.  
  13.         QTableWidgetItem *clone() const;
  14.         void setData(int role, const QVariant &value);
  15.         QVariant data(int role) const;
  16.         void setFormula(const QString &formula);
  17.         QString formula() const;
  18.         void setDirty();
  19.  
  20.     private:
  21.         QVariant value() const;
  22.         QVariant evalExpression(const QString &str, int &pos) const;
  23.         QVariant evalTerm(const QString &str, int &pos) const;
  24.         QVariant evalFactor(const QString &str, int &pos) const;
  25.  
  26.         mutable QVariant cachedValue;
  27.         mutable bool cacheIsDirty;
  28.     };
To copy to clipboard, switch view to plain text mode 
and here is its cell.cpp file :-
Qt Code: 
  1. #include "cell.h"
  2.     #include <QtWidgets>
  3.  
  4.     Cell::Cell()
  5.     {
  6.         setDirty();
  7.     }
  8.  
  9.     QTableWidgetItem *Cell::clone() const
  10.     {
  11.         return new Cell(*this);
  12.     }
  13.  
  14.     void Cell::setData(int role, const QVariant &value)
  15.     {
  16.         QTableWidgetItem::setData(role, value);
  17.         if(role == Qt::EditRole)
  18.         {
  19.             setDirty();
  20.         }
  21.     }   
  22.  
  23.     QString Cell::formula() const
  24.     {
  25.         return data(Qt::EditRole).toString();
  26.     }
  27.  
  28.     const QVariant Invalid;
  29.  
  30.     QVariant Cell::data(int role) const
  31.     {
  32.         if(role == Qt::DisplayRole)
  33.         {
  34.             if(this->value().isValid())
  35.             return value().toString();
  36.         else
  37.             return "####";
  38.         }
  39.         else if(role == Qt::TextAlignmentRole)
  40.         {
  41.             if(this->value().type() == QVariant::String)
  42.                 return int(Qt::AlignCenter| Qt::AlignVCenter);
  43.             else
  44.                 return int(Qt::AlignRight | Qt::AlignVCenter);
  45.         }
  46.         else
  47.         {
  48.             return QTableWidgetItem::data(role);
  49.         }
  50.     }
  51.  
  52.     void Cell::setFormula(const QString &formula)
  53.     {
  54.         setData(Qt::EditRole, formula);
  55.     }
  56.  
  57.     void Cell::setDirty()
  58.     {
  59.         this->cacheIsDirty = true;
  60.     }
  61.  
  62.     QVariant Cell::value() const
  63.     {
  64.         if (cacheIsDirty)
  65.         {
  66.             cacheIsDirty = false;
  67.  
  68.             QString formulaStr = formula();
  69.             if (formulaStr.startsWith('\''))
  70.             {
  71.                 cachedValue = formulaStr.mid(1);
  72.             }
  73.             else if (formulaStr.startsWith('='))
  74.             {
  75.                 cachedValue = Invalid;
  76.                 QString expr = formulaStr.mid(1);
  77.                 expr.replace(" ", "");
  78.                 expr.append(QChar::Null);
  79.  
  80.                 int pos = 0;
  81.                 cachedValue = evalExpression(expr, pos);
  82.                 if (expr[pos] != QChar::Null)
  83.                     cachedValue = Invalid;
  84.             }
  85.             else
  86.             {
  87.                 bool ok;
  88.                 double d = formulaStr.toDouble(&ok);
  89.                 if (ok)
  90.                 {
  91.                     cachedValue = d;
  92.                 }
  93.                 else
  94.                 {
  95.                     cachedValue = formulaStr;
  96.                 }
  97.             }
  98.         }
  99.         return cachedValue;
  100.     }
  101.  
  102.     QVariant Cell::evalExpression(const QString &str, int &pos) const
  103.     {      
  104.         QVariant result = evalTerm(str, pos);
  105.         while (str[pos] != QChar::Null)
  106.         {
  107.             QChar op = str[pos];
  108.             if (op != '+' && op != '-')
  109.                 return result;
  110.             ++pos;
  111.  
  112.             QVariant term = evalTerm(str, pos);
  113.             if (result.type() == QVariant::Double
  114.                     && term.type() == QVariant::Double) 
  115.             {
  116.                 if (op == '+') 
  117.                 {
  118.                     result = result.toDouble() + term.toDouble();
  119.                 }
  120.                  else 
  121.                  {
  122.                     result = result.toDouble() - term.toDouble();
  123.                  }
  124.             }
  125.             else 
  126.             {
  127.                 result = Invalid;
  128.             }   
  129.         }
  130.         return result;
  131.     }
  132.  
  133.     QVariant Cell::evalTerm(const QString &str, int &pos) const
  134.     {
  135.         QVariant result = evalFactor(str, pos);
  136.         while (str[pos] != QChar::Null) 
  137.         {
  138.             QChar op = str[pos];
  139.             if (op != '*' && op != '/')
  140.                 return result;
  141.             ++pos;
  142.  
  143.             QVariant factor = evalFactor(str, pos);
  144.             if (result.type() == QVariant::Double
  145.                     && factor.type() == QVariant::Double) 
  146.             {
  147.                 if (op == '*') 
  148.                 {
  149.                     result = result.toDouble() * factor.toDouble();
  150.                 }
  151.                 else 
  152.                 {
  153.                     if (factor.toDouble() == 0.0) 
  154.                     {
  155.                         result = Invalid;
  156.                     } 
  157.                     else 
  158.                     {
  159.                         result = result.toDouble() / factor.toDouble();
  160.                     }
  161.                  }
  162.              } 
  163.              else 
  164.              {
  165.                 result = Invalid;
  166.               }
  167.             }
  168.         return result;
  169.         }
  170.  
  171.  
  172.     QVariant Cell::evalFactor(const QString &str, int &pos) const
  173.     {
  174.         QVariant result;
  175.         bool negative = false;
  176.  
  177.         if (str[pos] == '-') 
  178.         {
  179.             negative = true;
  180.             ++pos;
  181.         }
  182.  
  183.         if (str[pos] == '(') 
  184.         {
  185.             ++pos;
  186.             result = evalExpression(str, pos);
  187.             if (str[pos] != ')')
  188.                 result = Invalid;
  189.             ++pos;
  190.         } 
  191.         else 
  192.         {
  193.             QRegExp regExp("[A-Za-z][1-9][0-9]{0,2}");
  194.             QString token;
  195.  
  196.             while (str[pos].isLetterOrNumber() || str[pos] == '.') 
  197.             {
  198.                 token += str[pos];
  199.                 ++pos;
  200.             }
  201.  
  202.         if (regExp.exactMatch(token)) 
  203.         {
  204.             int column = token[0].toUpper().unicode() - 'A';
  205.             int row = token.mid(1).toInt() - 1;
  206.  
  207.             Cell *c = static_cast<Cell *>(
  208.                               tableWidget()->item(row, column));
  209.             if (c) 
  210.             {
  211.                 result = c->value();
  212.             } 
  213.             else 
  214.             {
  215.                 result = 0.0;
  216.             }
  217.          } 
  218.          else 
  219.          {
  220.             bool ok;
  221.             result = token.toDouble(&ok);
  222.             if (!ok)
  223.                 result = Invalid;
  224.           }
  225.         }
  226.  
  227.         if (negative) 
  228.         {
  229.             if (result.type() == QVariant::Double) 
  230.             {
  231.                 result = -result.toDouble();
  232.             } 
  233.             else 
  234.             {
  235.             result = Invalid;
  236.             }
  237.         }
  238.      return result;
  239.     }
To copy to clipboard, switch view to plain text mode 
output is :- spsheet_mine.png
and output should be :- spsheet_book.png

of course i have not implemented toolbar but remaining should work.
how to remove error :-
No relevant classes found. No output generated