Base: Units: introduce unit one

Dimensionless quantities have all exponents equal to zero.
Such quantities are simply numbers. The associated unit is
the unit one, symbol 1, although this is rarely explicitly
written.

See chapter 2.3.3 Dimensions of quantities, The International
System of Units, 9th edition.

src/App/PropertyGeo.cpp

@@ -194,7 +194,7 @@ void PropertyVector::getPaths(std::vector<ObjectIdentifier>& paths) const
 const boost::any PropertyVector::getPathValue(const ObjectIdentifier& path) const
 {
     Base::Unit unit = getUnit();
-    if (!unit.isEmpty()) {
+    if (unit != Unit::One) {
         std::string p = path.getSubPathStr();
         if (p == ".x" || p == ".y" || p == ".z") {
             // Convert double to quantity
@@ -207,7 +207,7 @@ const boost::any PropertyVector::getPathValue(const ObjectIdentifier& path) cons
 bool PropertyVector::getPyPathValue(const ObjectIdentifier& path, Py::Object& res) const
 {
     Base::Unit unit = getUnit();
-    if (unit.isEmpty()) {
+    if (unit == Unit::One) {
         return false;
     }
 

src/Base/Quantity.cpp

@@ -270,10 +270,10 @@ std::string Quantity::getSafeUserString() const
     return Tools::escapeQuotesFromString(userStr);
 }
 
-/// true if it has a number without a unit
+/// true if unit equals to 1, therefore quantity has no dimension
 bool Quantity::isDimensionless() const
 {
-    return myUnit.isEmpty();
+    return myUnit == Unit::One;
 }
 
 /// true if it has a specific unit or no dimension.

src/Base/Unit.cpp

@@ -281,11 +281,6 @@ int Unit::angle() const
     return sig.Angle;
 }
 
-bool Unit::isEmpty() const
-{
-    return Val == 0;
-}
-
 int Unit::operator [](int index) const
 {
     UnitSignature sig;
@@ -318,6 +313,11 @@ bool Unit::operator ==(const Unit& that) const
     return Val == that.Val;
 }
 
+bool Unit::operator !=(const Unit& that) const
+{
+    return Val != that.Val;
+}
+
 Unit Unit::operator *(const Unit &right) const
 {
     Unit result;
@@ -360,7 +360,7 @@ Unit Unit::operator /(const Unit &right) const
 
 std::string Unit::getString() const
 {
-    if (isEmpty()) {
+    if (Val == 0) {
         return {};
     }
 
@@ -658,6 +658,8 @@ std::string Unit::getTypeString() const
     return spec->second;
 }
 
+const Unit Unit::One                        (0, 0, 0, 0, 0, 0, 0, 0);
+
 // SI base units
 const Unit Unit::AmountOfSubstance          (0, 0, 0, 0, 0, 1);
 const Unit Unit::ElectricCurrent            (0, 0, 0, 1);

src/Base/Unit.h

@@ -61,10 +61,7 @@ public:
     Unit operator*(const Unit&) const;
     Unit operator/(const Unit&) const;
     bool operator==(const Unit&) const;
-    bool operator!=(const Unit& that) const
-    {
-        return !(*this == that);
-    }
+    bool operator!=(const Unit& that) const;
     Unit& operator=(const Unit&) = default;
     Unit& operator=(Unit&&) = default;
     Unit pow(double exp) const;
@@ -79,7 +76,6 @@ public:
     int amountOfSubstance() const;
     int luminousIntensity() const;
     int angle() const;
-    bool isEmpty() const;
 
     std::string getString() const;
     /// get the type as an string such as "Area", "Length" or "Pressure".
@@ -87,6 +83,7 @@ public:
 
     /** Predefined Unit types. */
     //@{
+    static const Unit One;
     /// Length unit
     static const Unit Length;
     /// Mass unit

src/Gui/Dialogs/DlgExpressionInput.cpp

@@ -294,7 +294,7 @@ void DlgExpressionInput::checkExpression(const QString& text)
                 }
 
                 auto msg = value.getUserString();
-                if (!impliedUnit.isEmpty()) {
+                if (impliedUnit != Base::Unit::One) {
                     if (!value.isDimensionless() && value.getUnit() != impliedUnit)
                         throw Base::UnitsMismatchError("Unit mismatch between result and required unit");
 

src/Gui/InputField.cpp

@@ -282,7 +282,7 @@ void InputField::newInput(const QString & text)
         res.setUnit(this->actUnit);
 
     // check if unit fits!
-    if (!actUnit.isEmpty() && !res.isDimensionless() && actUnit != res.getUnit()){
+    if (actUnit != Unit::One && !res.isDimensionless() && actUnit != res.getUnit()){
         if (iconLabel->isHidden()) {
             iconLabel->setVisible(true);
         }

src/Mod/Spreadsheet/App/Cell.cpp

@@ -607,7 +607,7 @@ void Cell::setComputedUnit(const Base::Unit& unit)
     PropertySheet::AtomicPropertyChange signaller(*owner);
 
     computedUnit = unit;
-    setUsed(COMPUTED_UNIT_SET, !computedUnit.isEmpty());
+    setUsed(COMPUTED_UNIT_SET, computedUnit != Unit::One);
     setDirty();
 
     signaller.tryInvoke();
@@ -1110,7 +1110,7 @@ std::string Cell::getFormattedQuantity()
         const Base::Unit& computedUnit = floatProp->getUnit();
         qFormatted = QLocale().toString(rawVal, 'f', Base::UnitsApi::getDecimals());
         if (hasDisplayUnit) {
-            if (computedUnit.isEmpty() || computedUnit == du.unit) {
+            if (computedUnit == Unit::One || computedUnit == du.unit) {
                 QString number =
                     QLocale().toString(rawVal / duScale, 'f', Base::UnitsApi::getDecimals());
                 qFormatted = number + QString::fromStdString(" " + displayUnit.stringRep);

src/Mod/Spreadsheet/App/Sheet.cpp

@@ -802,7 +802,7 @@ void Sheet::updateProperty(CellAddress key)
                 Base::PyGILStateLocker lock;
                 setObjectProperty(key, constant->getPyValue());
             }
-            else if (!number->getUnit().isEmpty()) {
+            else if (number->getUnit() != Unit::One) {
                 setQuantityProperty(key, number->getValue(), number->getUnit());
             }
             else if (number->isInteger(&l)) {

src/Mod/Spreadsheet/Gui/SheetModel.cpp

@@ -384,7 +384,7 @@ QVariant SheetModel::data(const QModelIndex& index, int role) const
 
                 // Display locale specific decimal separator (#0003875,#0003876)
                 if (cell->getDisplayUnit(displayUnit)) {
-                    if (computedUnit.isEmpty() || computedUnit == displayUnit.unit) {
+                    if (computedUnit == Base::Unit::One || computedUnit == displayUnit.unit) {
                         QString number =
                             QLocale().toString(floatProp->getValue() / displayUnit.scaler,
                                                'f',

tests/src/Base/Unit.cpp

@@ -121,7 +121,7 @@ TEST(Unit, TestPowNoDim)
 {
     Base::Unit unit {};
     EXPECT_EQ(unit.pow(2), Base::Unit {0});
-    EXPECT_EQ(unit.isEmpty(), true);
+    EXPECT_EQ(unit == Base::Unit::One, true);
 }
 
 TEST(Unit, TestPowEQ1)