replace SW602Variable by boost::optional

5 files changed, 125 insertions, 181 deletions

diff --git a/src/lib/SW602Font.cpp b/src/lib/SW602Font.cpp
index 5d56239..42c86b3 100644
--- a/src/lib/SW602Font.cpp
+++ b/src/lib/SW602Font.cpp
@@ -62,7 +62,7 @@ std::ostream &operator<<(std::ostream &o, SW602Font::Line const &line)
   if (line.m_word) o << ":byword";
   if (line.m_width < 1.0 || line.m_width > 1.0)
     o << ":w=" << line.m_width ;
-  if (line.m_color.isSet())
+  if (line.m_color)
     o << ":col=" << line.m_color.get();
   return o;
 }
@@ -103,7 +103,7 @@ void SW602Font::Line::addTo(librevenge::RVNGPropertyList &propList, std::string
   default:
     break;
   }
-  if (m_color.isSet())
+  if (m_color)
   {
     s.str("");
     s << "style:text-" << type << "-color";
@@ -166,7 +166,7 @@ std::string SW602Font::getDebugString() const
     o << "id=" << id() << ",";
   }
   if (size() > 0) o << "sz=" << size() << ",";
-  if (m_deltaSpacing.isSet())
+  if (m_deltaSpacing)
   {
     if (m_deltaSpacingUnit.get()==librevenge::RVNG_PERCENT)
       o << "extend/condensed=" << m_deltaSpacing.get() << "%,";
@@ -175,11 +175,11 @@ std::string SW602Font::getDebugString() const
     else if (m_deltaSpacing.get() < 0)
       o << "condensed=" << -m_deltaSpacing.get() << ",";
   }
-  if (m_widthStreching.isSet())
+  if (m_widthStreching)
     o << "scaling[width]=" <<  m_widthStreching.get()*100.f << "%,";
-  if (m_scriptPosition.isSet() && m_scriptPosition.get().isSet())
+  if (m_scriptPosition && m_scriptPosition.get().isSet())
     o << "script=" << m_scriptPosition.get().str(size()) << ",";
-  if (m_flags.isSet() && m_flags.get())
+  if (m_flags && m_flags.get())
   {
     o << "fl=";
     uint32_t flag = m_flags.get();
@@ -200,17 +200,17 @@ std::string SW602Font::getDebugString() const
     if (flag&reverseWritingBit) o << "reverseWriting:";
     o << ",";
   }
-  if (m_overline.isSet() && m_overline->isSet())
+  if (m_overline && m_overline->isSet())
     o << "overline=[" << m_overline.get() << "],";
-  if (m_strikeoutline.isSet() && m_strikeoutline->isSet())
+  if (m_strikeoutline && m_strikeoutline->isSet())
     o << "strikeOut=[" << m_strikeoutline.get() << "],";
-  if (m_underline.isSet() && m_underline->isSet())
+  if (m_underline && m_underline->isSet())
     o << "underline=[" << m_underline.get() << "],";
   if (hasColor())
     o << "col=" << m_color.get()<< ",";
-  if (m_backgroundColor.isSet() && !m_backgroundColor.get().isWhite())
+  if (m_backgroundColor && !m_backgroundColor.get().isWhite())
     o << "backCol=" << m_backgroundColor.get() << ",";
-  if (m_language.isSet() && m_language.get().length())
+  if (m_language && m_language.get().length())
     o << "lang=" << m_language.get() << ",";
   o << m_extra;
   return o.str();
@@ -259,29 +259,29 @@ void SW602Font::addTo(librevenge::RVNGPropertyList &pList) const
   else if (attributeBits & engraveBit)
     pList.insert("style:font-relief", "engraved");
 
-  if (m_scriptPosition.isSet() && m_scriptPosition->isSet())
+  if (m_scriptPosition && m_scriptPosition->isSet())
   {
     std::string pos=m_scriptPosition->str(fSize);
     if (pos.length())
       pList.insert("style:text-position", pos.c_str());
   }
 
-  if (m_overline.isSet() && m_overline->isSet())
+  if (m_overline && m_overline->isSet())
     m_overline->addTo(pList, "overline");
-  if (m_strikeoutline.isSet() && m_strikeoutline->isSet())
+  if (m_strikeoutline && m_strikeoutline->isSet())
     m_strikeoutline->addTo(pList, "line-through");
-  if (m_underline.isSet() && m_underline->isSet())
+  if (m_underline && m_underline->isSet())
     m_underline->addTo(pList, "underline");
   if ((attributeBits & boxedBit) || (attributeBits & boxedRoundedBit))
   {
     // do minimum: add a overline and a underline box
     Line simple(Line::Simple);
-    if (!m_overline.isSet() || !m_overline->isSet())
+    if (!m_overline || !m_overline->isSet())
       simple.addTo(pList, "overline");
-    if (!m_underline.isSet() || !m_underline->isSet())
+    if (!m_underline || !m_underline->isSet())
       simple.addTo(pList, "underline");
   }
-  if (m_deltaSpacing.isSet())
+  if (m_deltaSpacing)
   {
     if (m_deltaSpacingUnit.get()==librevenge::RVNG_PERCENT)
     {
@@ -295,7 +295,7 @@ void SW602Font::addTo(librevenge::RVNGPropertyList &pList) const
     else if (m_deltaSpacing.get() < 0 || m_deltaSpacing.get()>0)
       pList.insert("fo:letter-spacing", m_deltaSpacing.get(), librevenge::RVNG_POINT);
   }
-  if (m_widthStreching.isSet() && m_widthStreching.get() > 0.0 &&
+  if (m_widthStreching && m_widthStreching.get() > 0.0 &&
       (m_widthStreching.get()>1.0||m_widthStreching.get()<1.0))
     pList.insert("style:text-scale", m_widthStreching.get(), librevenge::RVNG_PERCENT);
   if (attributeBits & reverseVideoBit)
@@ -306,10 +306,10 @@ void SW602Font::addTo(librevenge::RVNGPropertyList &pList) const
   else
   {
     pList.insert("fo:color", m_color->str().c_str());
-    if (m_backgroundColor.isSet() && !m_backgroundColor->isWhite())
+    if (m_backgroundColor && !m_backgroundColor->isWhite())
       pList.insert("fo:background-color", m_backgroundColor->str().c_str());
   }
-  if (m_language.isSet())
+  if (m_language)
   {
     size_t len=m_language->length();
     std::string lang(m_language.get());
diff --git a/src/lib/SW602Font.h b/src/lib/SW602Font.h
index 524d05f..9d25c36 100644
--- a/src/lib/SW602Font.h
+++ b/src/lib/SW602Font.h
@@ -13,6 +13,8 @@
 #include <string>
 #include <vector>
 
+#include <boost/optional.hpp>
+
 #include "SW602Types.h"
 
 namespace libsw602
@@ -59,8 +61,8 @@ public:
       if (m_word != oth.m_word) return m_word ? -1 : 1;
       if (m_width < oth.m_width) return -1;
       if (m_width > oth.m_width) return 1;
-      if (m_color.isSet() != oth.m_color.isSet())
-        return m_color.isSet();
+      if (m_color != oth.m_color)
+        return bool(m_color);
       if (m_color.get() < oth.m_color.get()) return -1;
       if (m_color.get() > oth.m_color.get()) return 1;
       return 0;
@@ -74,7 +76,7 @@ public:
     /** the width in point */
     float m_width;
     /** the color ( if not set, we use the font color )*/
-    SW602Variable<SW602Color> m_color;
+    boost::optional<SW602Color> m_color;
   };
   /** a small struct to define the script position in SW602Font */
   struct Script
@@ -183,28 +185,38 @@ public:
   //! returns true if the font id is initialized
   bool isSet() const
   {
-    return m_id.isSet();
+    return m_id;
   }
   //! inserts the set value in the current font
   void insert(SW602Font const &ft)
   {
-    m_id.insert(ft.m_id);
-    m_size.insert(ft.m_size);
-    m_deltaSpacing.insert(ft.m_deltaSpacing);
-    m_deltaSpacingUnit.insert(ft.m_deltaSpacingUnit);
-    m_widthStreching.insert(ft.m_widthStreching);
-    m_scriptPosition.insert(ft.m_scriptPosition);
-    if (ft.m_flags.isSet())
+    if (ft.m_id)
+      m_id = ft.m_id;
+    if (ft.m_size)
+      m_size = ft.m_size;
+    if (ft.m_deltaSpacing)
+      m_deltaSpacing = ft.m_deltaSpacing;
+    if (ft.m_deltaSpacingUnit)
+      m_deltaSpacingUnit = ft.m_deltaSpacingUnit;
+    if (ft.m_widthStreching)
+      m_widthStreching = ft.m_widthStreching;
+    if (ft.m_scriptPosition)
+      m_scriptPosition = ft.m_scriptPosition;
+    if (ft.m_flags)
     {
-      if (m_flags.isSet())
+      if (m_flags)
         setFlags(flags()| ft.flags());
       else
         m_flags = ft.m_flags;
     }
-    m_overline.insert(ft.m_overline);
-    m_strikeoutline.insert(ft.m_strikeoutline);
-    m_underline.insert(ft.m_underline);
-    m_color.insert(ft.m_color);
+    if (ft.m_overline)
+      m_overline = ft.m_overline;
+    if (ft.m_strikeoutline)
+      m_strikeoutline = ft.m_strikeoutline;
+    if (ft.m_underline)
+      m_underline = ft.m_underline;
+    if (ft.m_color)
+      m_color = ft.m_color;
     m_extra += ft.m_extra;
   }
   //! sets the font id and resets size to the previous size for this font
@@ -288,7 +300,7 @@ public:
   //! returns true if the font color is not black
   bool hasColor() const
   {
-    return m_color.isSet() && !m_color.get().isBlack();
+    return m_color && !m_color.get().isBlack();
   }
   //! returns the font color
   void getColor(SW602Color &c) const
@@ -321,16 +333,16 @@ public:
   //! return true if the font has decorations line (overline, strikeout, underline)
   bool hasDecorationLines() const
   {
-    return (m_overline.isSet() && m_overline->isSet()) ||
-           (m_strikeoutline.isSet() && m_strikeoutline->isSet()) ||
-           (m_underline.isSet() && m_underline->isSet());
+    return (m_overline && m_overline->isSet()) ||
+           (m_strikeoutline && m_strikeoutline->isSet()) ||
+           (m_underline && m_underline->isSet());
   }
   //! reset the decoration
   void resetDecorationLines()
   {
-    if (m_overline.isSet()) m_overline=Line(Line::None);
-    if (m_strikeoutline.isSet()) m_strikeoutline=Line(Line::None);
-    if (m_underline.isSet()) m_underline=Line(Line::None);
+    if (m_overline) m_overline=Line(Line::None);
+    if (m_strikeoutline) m_strikeoutline=Line(Line::None);
+    if (m_underline) m_underline=Line(Line::None);
   }
   //! returns the overline
   Line const &getOverline() const
@@ -509,19 +521,19 @@ public:
   }
 
 protected:
-  SW602Variable<int> m_id /** font identificator*/;
-  SW602Variable<float> m_size /** font size */;
-  SW602Variable<float> m_deltaSpacing /** expand(&gt; 0), condensed(&lt; 0) depl*/;
-  SW602Variable<librevenge::RVNGUnit> m_deltaSpacingUnit /** the delta spacing unit */;
-  SW602Variable<float> m_widthStreching /** the width streching in percent */;
-  SW602Variable<Script> m_scriptPosition /** the sub/super script definition */;
-  SW602Variable<uint32_t> m_flags /** font attributes */;
-  SW602Variable<Line> m_overline /** overline attributes */;
-  SW602Variable<Line> m_strikeoutline /** overline attributes */;
-  SW602Variable<Line> m_underline /** underline attributes */;
-  SW602Variable<SW602Color> m_color /** font color */;
-  SW602Variable<SW602Color> m_backgroundColor /** font background color */;
-  SW602Variable<std::string> m_language /** the language if set */;
+  boost::optional<int> m_id /** font identificator*/;
+  boost::optional<float> m_size /** font size */;
+  boost::optional<float> m_deltaSpacing /** expand(&gt; 0), condensed(&lt; 0) depl*/;
+  boost::optional<librevenge::RVNGUnit> m_deltaSpacingUnit /** the delta spacing unit */;
+  boost::optional<float> m_widthStreching /** the width streching in percent */;
+  boost::optional<Script> m_scriptPosition /** the sub/super script definition */;
+  boost::optional<uint32_t> m_flags /** font attributes */;
+  boost::optional<Line> m_overline /** overline attributes */;
+  boost::optional<Line> m_strikeoutline /** overline attributes */;
+  boost::optional<Line> m_underline /** underline attributes */;
+  boost::optional<SW602Color> m_color /** font color */;
+  boost::optional<SW602Color> m_backgroundColor /** font background color */;
+  boost::optional<std::string> m_language /** the language if set */;
 public:
   //! extra data
   std::string m_extra;
diff --git a/src/lib/SW602Paragraph.cpp b/src/lib/SW602Paragraph.cpp
index 2264692..86fdd83 100644
--- a/src/lib/SW602Paragraph.cpp
+++ b/src/lib/SW602Paragraph.cpp
@@ -129,8 +129,8 @@ SW602Paragraph::SW602Paragraph() : m_marginsUnit(librevenge::RVNG_INCH), m_spaci
   m_spacings[0] = 1.0; // interline normal
   for (int i = 0; i < 3; i++)
   {
-    m_margins[i].setSet(false);
-    m_spacings[i].setSet(false);
+    m_margins[i].reset();
+    m_spacings[i].reset();
   }
 }
 
@@ -183,8 +183,8 @@ int SW602Paragraph::cmp(SW602Paragraph const &para) const
   if (m_borders.size() > para.m_borders.size()) return 1;
   for (size_t i=0; i < m_borders.size(); i++)
   {
-    if (m_borders[i].isSet() != para.m_borders[i].isSet())
-      return m_borders[i].isSet() ? 1 : -1;
+    if (bool(m_borders[i]) != bool(para.m_borders[i]))
+      return m_borders[i] ? 1 : -1;
     diff = m_borders[i]->compare(*(para.m_borders[i]));
     if (diff) return diff;
   }
@@ -197,13 +197,18 @@ void SW602Paragraph::insert(SW602Paragraph const &para)
 {
   for (int i = 0; i < 3; i++)
   {
-    m_margins[i].insert(para.m_margins[i]);
-    m_spacings[i].insert(para.m_spacings[i]);
+    if (para.m_margins[i])
+      m_margins[i] = para.m_margins[i];
+    if (para.m_spacings[i])
+      m_spacings[i] = para.m_spacings[i];
   }
-  m_marginsUnit.insert(para.m_marginsUnit);
-  m_spacingsInterlineUnit.insert(para.m_spacingsInterlineUnit);
-  m_spacingsInterlineType.insert(para.m_spacingsInterlineType);
-  if (para.m_tabs.isSet() && m_tabs.isSet())
+  if (para.m_marginsUnit)
+    m_marginsUnit = para.m_marginsUnit;
+  if (para.m_spacingsInterlineUnit)
+    m_spacingsInterlineUnit = para.m_spacingsInterlineUnit;
+  if (para.m_spacingsInterlineType)
+    m_spacingsInterlineType = para.m_spacingsInterlineType;
+  if (para.m_tabs && m_tabs)
   {
     std::map<double, SW602TabStop> all;
     for (size_t t=0; t <m_tabs->size(); ++t)
@@ -216,20 +221,29 @@ void SW602Paragraph::insert(SW602Paragraph const &para)
     for (; it!=all.end(); ++it)
       m_tabs->push_back(it->second);
   }
-  else if (para.m_tabs.isSet())
+  else if (para.m_tabs)
     m_tabs=para.m_tabs;
-  m_tabsRelativeToLeftMargin.insert(para.m_tabsRelativeToLeftMargin);
-  m_justify.insert(para.m_justify);
-  m_breakStatus.insert(para.m_breakStatus);
-  m_listLevelIndex.insert(para.m_listLevelIndex);
-  m_listId.insert(para.m_listId);
-  m_listStartValue.insert(m_listStartValue);
-  m_listLevel.insert(para.m_listLevel);
-  m_backgroundColor.insert(para.m_backgroundColor);
+  if (para.m_tabsRelativeToLeftMargin)
+    m_tabsRelativeToLeftMargin = para.m_tabsRelativeToLeftMargin;
+  if (para.m_justify)
+    m_justify = para.m_justify;
+  if (para.m_breakStatus)
+    m_breakStatus = para.m_breakStatus;
+  if (para.m_listLevelIndex)
+    m_listLevelIndex = para.m_listLevelIndex;
+  if (para.m_listId)
+    m_listId = para.m_listId;
+  if (m_listStartValue)
+    m_listStartValue = m_listStartValue;
+  if (para.m_listLevel)
+    m_listLevel = para.m_listLevel;
+  if (para.m_backgroundColor)
+    m_backgroundColor = para.m_backgroundColor;
   if (m_borders.size() < para.m_borders.size())
     m_borders.resize(para.m_borders.size());
   for (size_t i = 0; i < para.m_borders.size(); i++)
-    m_borders[i].insert(para.m_borders[i]);
+    if (para.m_borders[i])
+      m_borders[i] = para.m_borders[i];
   m_styleName=para.m_styleName; // checkme
   m_extra += para.m_extra;
 }
@@ -238,7 +252,7 @@ bool SW602Paragraph::hasBorders() const
 {
   for (size_t i = 0; i < m_borders.size() && i < 4; i++)
   {
-    if (!m_borders[i].isSet())
+    if (!m_borders[i])
       continue;
     if (!m_borders[i]->isEmpty())
       return true;
@@ -252,7 +266,7 @@ bool SW602Paragraph::hasDifferentBorders() const
   if (m_borders.size() < 4) return true;
   for (size_t i = 1; i < m_borders.size(); i++)
   {
-    if (m_borders[i].isSet() != m_borders[0].isSet())
+    if (bool(m_borders[i]) != bool(m_borders[0]))
       return true;
     if (*(m_borders[i]) != *(m_borders[0]))
       return true;
@@ -306,7 +320,7 @@ void SW602Paragraph::addTo(librevenge::RVNGPropertyList &propList, bool inTable)
       {
         if (w && setAll)
           break;
-        if (!m_borders[w].isSet())
+        if (!m_borders[w])
           continue;
         SW602Border const &border = *(m_borders[w]);
         if (border.isEmpty())
@@ -467,7 +481,7 @@ std::ostream &operator<<(std::ostream &o, SW602Paragraph const &pp)
 
   for (size_t i = 0; i < pp.m_borders.size(); i++)
   {
-    if (!pp.m_borders[i].isSet())
+    if (!pp.m_borders[i])
       continue;
     SW602Border const &border = pp.m_borders[i].get();
     if (border.isEmpty())
diff --git a/src/lib/SW602Paragraph.h b/src/lib/SW602Paragraph.h
index 2622847..97bbf00 100644
--- a/src/lib/SW602Paragraph.h
+++ b/src/lib/SW602Paragraph.h
@@ -13,6 +13,8 @@
 #include <iostream>
 #include <vector>
 
+#include <boost/optional.hpp>
+
 #include <librevenge/librevenge.h>
 
 #include "SW602List.h"
@@ -97,7 +99,7 @@ public:
   {
     SW602Border empty;
     empty.m_style=SW602Border::None;
-    m_borders.resize(newSize, SW602Variable<SW602Border>(empty));
+    m_borders.resize(newSize, boost::optional<SW602Border>(empty));
   }
   //! set the interline
   void setInterline(double value, librevenge::RVNGUnit unit, LineSpacingType type=Fixed)
@@ -119,43 +121,43 @@ public:
    * - 0: first line left margin
    * - 1: left margin
    * - 2: right margin*/
-  SW602Variable<double> m_margins[3]; // 0: first line left, 1: left, 2: right
+  boost::optional<double> m_margins[3]; // 0: first line left, 1: left, 2: right
   /** the margins INCH, ... */
-  SW602Variable<librevenge::RVNGUnit> m_marginsUnit;
+  boost::optional<librevenge::RVNGUnit> m_marginsUnit;
   /** the line spacing
    *
    * - 0: interline
    * - 1: before
    * - 2: after */
-  SW602Variable<double> m_spacings[3]; // 0: interline, 1: before, 2: after
+  boost::optional<double> m_spacings[3]; // 0: interline, 1: before, 2: after
   /** the interline unit PERCENT or INCH, ... */
-  SW602Variable<librevenge::RVNGUnit> m_spacingsInterlineUnit;
+  boost::optional<librevenge::RVNGUnit> m_spacingsInterlineUnit;
   /** the interline type: fixed, atLeast, ... */
-  SW602Variable<LineSpacingType> m_spacingsInterlineType;
+  boost::optional<LineSpacingType> m_spacingsInterlineType;
   //! the tabulations
-  SW602Variable<std::vector<SW602TabStop> > m_tabs;
+  boost::optional<std::vector<SW602TabStop> > m_tabs;
   //! true if the tabs are relative to left margin, false if there are relative to the page margin (default)
-  SW602Variable<bool> m_tabsRelativeToLeftMargin;
+  boost::optional<bool> m_tabsRelativeToLeftMargin;
 
   /** the justification */
-  SW602Variable<Justification> m_justify;
+  boost::optional<Justification> m_justify;
   /** a list of bits: 0x1 (unbreakable), 0x2 (do not break after) */
-  SW602Variable<int> m_breakStatus; // BITS: 1: unbreakable, 2: dont break after
+  boost::optional<int> m_breakStatus; // BITS: 1: unbreakable, 2: dont break after
 
   /** the actual level index */
-  SW602Variable<int> m_listLevelIndex;
+  boost::optional<int> m_listLevelIndex;
   /** the list id (if know ) */
-  SW602Variable<int> m_listId;
+  boost::optional<int> m_listId;
   /** the list start value (if set ) */
-  SW602Variable<int> m_listStartValue;
+  boost::optional<int> m_listStartValue;
   /** the actual level */
-  SW602Variable<SW602ListLevel> m_listLevel;
+  boost::optional<SW602ListLevel> m_listLevel;
 
   //! the background color
-  SW602Variable<SW602Color> m_backgroundColor;
+  boost::optional<SW602Color> m_backgroundColor;
 
   //! list of border ( order SW602Border::Pos)
-  std::vector<SW602Variable<SW602Border> > m_borders;
+  std::vector<boost::optional<SW602Border> > m_borders;
 
   //! the style name
   std::string m_styleName;
diff --git a/src/lib/SW602Types.h b/src/lib/SW602Types.h
index 5d1eafb..885dbc1 100644
--- a/src/lib/SW602Types.h
+++ b/src/lib/SW602Types.h
@@ -364,90 +364,6 @@ typedef boost::shared_ptr<SW602SubDocument> SW602SubDocumentPtr;
 //! a smart pointer of SW602TextListener
 typedef boost::shared_ptr<SW602TextListener> SW602TextListenerPtr;
 
-/** a generic variable template: value + flag to know if the variable is set
-
-\note the variable is considered set as soon a new value is set or
-when its content is acceded by a function which returns a not-const
-reference... You can use the function setSet to unset it.
-*/
-template <class T> struct SW602Variable
-{
-  //! constructor
-  SW602Variable() : m_data(), m_set(false) {}
-  //! constructor with a default value
-  explicit SW602Variable(T const &def) : m_data(def), m_set(false) {}
-  //! copy constructor
-  SW602Variable(SW602Variable const &orig) : m_data(orig.m_data), m_set(orig.m_set) {}
-  //! copy operator
-  SW602Variable &operator=(SW602Variable const &orig)
-  {
-    if (this != &orig)
-    {
-      m_data = orig.m_data;
-      m_set = orig.m_set;
-    }
-    return *this;
-  }
-  //! set a value
-  SW602Variable &operator=(T const &val)
-  {
-    m_data = val;
-    m_set = true;
-    return *this;
-  }
-  //! update the current value if orig is set
-  void insert(SW602Variable const &orig)
-  {
-    if (orig.m_set)
-    {
-      m_data = orig.m_data;
-      m_set = orig.m_set;
-    }
-  }
-  //! operator*
-  T const *operator->() const
-  {
-    return &m_data;
-  }
-  /** operator* */
-  T *operator->()
-  {
-    m_set = true;
-    return &m_data;
-  }
-  //! operator*
-  T const &operator*() const
-  {
-    return m_data;
-  }
-  //! operator*
-  T &operator*()
-  {
-    m_set = true;
-    return m_data;
-  }
-  //! return the current value
-  T const &get() const
-  {
-    return m_data;
-  }
-  //! return true if the variable is set
-  bool isSet() const
-  {
-    return m_set;
-  }
-  //! define if the variable is set
-  void setSet(bool newVal)
-  {
-    m_set=newVal;
-  }
-protected:
-  //! the value
-  T m_data;
-  //! a flag to know if the variable is set or not
-  bool m_set;
-};
-
 /* ---------- vec2/box2f ------------- */
 /*! \class SW602Vec2
  *   \brief small class which defines a vector with 2 elements