diff --git a/kcalc.h b/kcalc.h
index 7b35bdc..4e02638 100644
--- a/kcalc.h
+++ b/kcalc.h
@@ -1,290 +1,291 @@
 /*
 Copyright (C) 2001 - 2013 Evan Teran
                           evan.teran@gmail.com
 
 Copyright (C) 1996 - 2000 Bernd Johannes Wuebben
                           wuebben@kde.org
 
 This program is free software; you can redistribute it and/or
 modify it under the terms of the GNU General Public License as
 published by the Free Software Foundation; either version 2 of 
 the License, or (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #ifndef KCALC_H_
 #define KCALC_H_
 
 class Constants;
 class QButtonGroup;
+class QLabel;
 class KToggleAction;
 class KCalcConstMenu;
 class KCalcStatusBar;
 
 /*
   Kcalc basically consist of a class for the GUI (here), a class for
   the display (dlabel.h), and one for the mathematics core
   (kcalc_core.h).
 
   When for example '+' is pressed, one sends the contents of the
   Display and the '+' to the core via "core.Plus(DISPLAY_AMOUNT)".
   This only updates the core. To bring the changes to the display,
   use afterwards "UpdateDisplay(true)".
 
   "UpdateDisplay(true)" means that the amount to be displayed should
   be taken from the core (get the result of some operation that was
   performed), "UpdateDisplay(false)" has already the information, what
   to be display (e.g. user is typing in a number).  Note that in the
   last case the core does not know the number typed in until some
   operation button is pressed, e.g. "core.Plus(display_number)".
  */
 
 #include "kcalc_core.h"
 #include "kcalc_button.h"
 #include "kcalc_const_button.h"
 
 #include "ui_kcalc.h"
 #include "ui_general.h"
 #include "ui_fonts.h"
 #include "ui_constants.h"
 #include "ui_colors.h"
 
-
+#include <array>
 #include <kxmlguiwindow.h>
 
 class General: public QWidget, public Ui::General
 {
     Q_OBJECT
 public:
     explicit General(QWidget *parent) : QWidget(parent) {
         setupUi(this);
     }
 };
 
 class Fonts: public QWidget, public Ui::Fonts
 {
     Q_OBJECT
 public:
     explicit Fonts(QWidget *parent) : QWidget(parent) {
         setupUi(this);
     }
 };
 
 class Constants : public QWidget, public Ui::Constants
 {
     Q_OBJECT
 public:
     explicit Constants(QWidget *parent) : QWidget(parent) {
         setupUi(this);
     }
 };
 
 class Colors : public QWidget, public Ui::Colors
 {
     Q_OBJECT
 public:
     explicit Colors(QWidget *parent) : QWidget(parent) {
         setupUi(this);
     }
 };
 
 
 class KCalculator : public KXmlGuiWindow, private Ui::KCalculator
 {
     Q_OBJECT
 
 public:
     explicit KCalculator(QWidget *parent = nullptr);
     ~KCalculator();
 
 Q_SIGNALS:
     void switchShift(bool);
     void switchMode(ButtonModeFlags, bool);
     void switchShowAccels(bool);
 
 public:
     enum UpdateFlag {
         UPDATE_FROM_CORE    = 1,
         UPDATE_STORE_RESULT = 2
     };
     
     Q_DECLARE_FLAGS(UpdateFlags, UpdateFlag)
 
 private:
     bool eventFilter(QObject *o, QEvent *e) override;
     bool event(QEvent *e) override;
     void updateGeometry();
     void setupMainActions();
     void setupKeys();
 	void setupNumberKeys();
 	void setupRightKeypad();
 	void setupNumericKeypad();
 	void setupLogicKeys();
 	void setupScientificKeys();
 	void setupStatisticKeys();
 	void setupConstantsKeys();
 	void setupMiscKeys();
     void keyPressEvent(QKeyEvent *e) override;
     void keyReleaseEvent(QKeyEvent *e) override;
     void setPrecision();
     void setAngle();
     void setBase();
 
     void updateDisplay(UpdateFlags flags);
     KCalcStatusBar *statusBar();
 	
     // button sets
     void showMemButtons(bool toggled);
     void showStatButtons(bool toggled);
     void showScienceButtons(bool toggled);
     void showLogicButtons(bool toggled);
 	
 	KCalcConstMenu *createConstantsMenu();
 
 protected Q_SLOTS:
     void changeButtonNames();
     void updateSettings();
     void setColors();
     void setFonts();
     void EnterEqual();
     void showSettings();
 
     // Mode
     void slotSetSimpleMode();
     void slotSetScienceMode();
     void slotSetStatisticMode();
     void slotSetNumeralMode();
 
     void slotConstantsShow(bool toggled);
     void slotBitsetshow(bool toggled);
     void slotAngleSelected(int mode);
     void slotBaseSelected(int base);
     void slotNumberclicked(int number_clicked);
     void slotEEclicked();
     void slotShifttoggled(bool myboolean);
     void slotMemRecallclicked();
     void slotMemStoreclicked();
     void slotSinclicked();
     void slotPlusMinusclicked();
     void slotMemPlusMinusclicked();
     void slotCosclicked();
     void slotReciclicked();
     void slotTanclicked();
     void slotFactorialclicked();
     void slotLogclicked();
     void slotSquareclicked();
     void slotCubeclicked();
     void slotLnclicked();
     void slotPowerclicked();
     void slotMemClearclicked();
     void slotClearclicked();
     void slotAllClearclicked();
     void slotParenOpenclicked();
     void slotParenCloseclicked();
     void slotANDclicked();
     void slotMultiplicationclicked();
     void slotDivisionclicked();
     void slotORclicked();
     void slotXORclicked();
     void slotPlusclicked();
     void slotMinusclicked();
     void slotLeftShiftclicked();
     void slotRightShiftclicked();
     void slotPeriodclicked();
     void slotEqualclicked();
     void slotPercentclicked();
     void slotNegateclicked();
     void slotModclicked();
     void slotStatNumclicked();
     void slotStatMeanclicked();
     void slotStatStdDevclicked();
     void slotStatMedianclicked();
     void slotStatDataInputclicked();
     void slotStatClearDataclicked();
     void slotHyptoggled(bool flag);
     void slotConstclicked(int);
 	void slotBackspaceclicked();
 
     void slotConstantToDisplay(const science_constant &const_chosen);
     void slotChooseScientificConst0(const science_constant &);
     void slotChooseScientificConst1(const science_constant &);
     void slotChooseScientificConst2(const science_constant &);
     void slotChooseScientificConst3(const science_constant &);
     void slotChooseScientificConst4(const science_constant &);
     void slotChooseScientificConst5(const science_constant &);
 
     void slotBitsetChanged(quint64);
     void slotUpdateBitset(const KNumber &);
 
     void slotBaseModeAmountChanged(KNumber number);
 
 private:
     enum StatusField {
         ShiftField = 0,
         BaseField,
         AngleField,
         MemField
     };
 	
     enum AngleMode {
         DegMode = 0,
         RadMode,
         GradMode
     };
     
 	enum BaseMode {
         BinMode = 2,
         OctMode = 8,
         DecMode = 10,
         HexMode = 16
     };
 
 private:
     bool shift_mode_;
     bool hyp_mode_;
     KNumber memory_num_;
 
     int angle_mode_; // angle modes for trigonometric values
 
 	KCalcConstMenu* constants_menu_;
 
     Constants*          constants_; // this is the dialog for configuring const buttons
 
     QButtonGroup* angle_choose_group_;
     QButtonGroup*  base_choose_group_;
     // num_button_group_: 0-9 = digits, 0xA-0xF = hex-keys
     QButtonGroup*  num_button_group_;
 
     QList<QAbstractButton*> logic_buttons_;
     QList<QAbstractButton*> scientific_buttons_;
     QList<QAbstractButton*> stat_buttons_;
     QList<QAbstractButton*> const_buttons_;
 
     std::array<QLabel*, 4> base_conversion_labels_;
 
     KToggleAction *action_bitset_show_;
     KToggleAction *action_constants_show_;
 
     KToggleAction *action_mode_simple_;
     KToggleAction *action_mode_science_;
     KToggleAction *action_mode_statistic_;
     KToggleAction *action_mode_numeral_;
 
     QList<QAbstractButton*> function_button_list_;
     QList<QAbstractButton*> stat_button_list_;
     QList<QAbstractButton*> mem_button_list_;
     QList<QAbstractButton*> operation_button_list_;
 
     CalcEngine core;
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(KCalculator::UpdateFlags)
 
 #endif