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T73 CMeasurementUnit converter strategy based on function pointers.

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Because function pointers are literal types, so they can be constexpr.
This commit is contained in:
Mathew Sutcliffe
2017-04-21 02:06:03 +01:00
parent 895190c4d0
commit 48482d8d1e
2 changed files with 30 additions and 40 deletions
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4
src/blackmisc/pq/measurementunit.cpp
View File

@@ -32,8 +32,8 @@ namespace BlackMisc
double CMeasurementUnit::convertFrom(double value, const CMeasurementUnit &unit) const
{
if (this->isNull() || unit.isNull()) return 0;
if (this->m_converter == unit.m_converter) return value;
return this->m_converter->fromDefault(unit.m_converter->toDefault(value));
if (this->m_toDefault == unit.m_toDefault && this->m_fromDefault == unit.m_fromDefault) return value;
return this->m_fromDefault(unit.m_toDefault(value));
}
QString CMeasurementUnit::makeRoundedQStringWithUnit(double value, int digits, bool i18n) const

66
src/blackmisc/pq/measurementunit.h
View File

@@ -46,41 +46,26 @@ namespace BlackMisc
{
protected:
/*!
* Abstract strategy pattern that encapsulates a unit conversion strategy.
* Pointer to function for converting between units.
*/
class Converter : public QSharedData
{
public:
/*!
* Virtual destructor.
*/
virtual ~Converter() {}
/*!
* Convert from this unit to default unit.
*/
virtual double toDefault(double value) const = 0;
/*!
* Convert from default unit to this unit.
*/
virtual double fromDefault(double value) const = 0;
};
using ConverterFunction = double (*)(double);
/*!
* Converter for default values, such as None, used with public constructor
*/
struct NilConverter : public Converter
struct NilConverter
{
virtual double toDefault(double) const override { return 0.0; }
virtual double fromDefault(double) const override { return 0.0; }
static double toDefault(double) { return 0.0; } //!< convert from this unit to the default unit
static double fromDefault(double) { return 0.0; } //!< convert to this unit from the default unit
};
/*!
* Concrete strategy pattern for converting unit that does nothing.
*/
struct IdentityConverter : public Converter
struct IdentityConverter
{
virtual double toDefault(double value) const override { return value; }
virtual double fromDefault(double value) const override { return value; }
static double toDefault(double value) { return value; } //!< convert from this unit to the default unit
static double fromDefault(double value) { return value; } //!< convert to this unit from the default unit
};
/*!
@@ -88,10 +73,10 @@ namespace BlackMisc
* \tparam Policy a policy class with static method factor() returning double
*/
template <class Policy>
struct LinearConverter : public Converter
struct LinearConverter
{
virtual double toDefault(double value) const override { return value * Policy::factor(); }
virtual double fromDefault(double value) const override { return value / Policy::factor(); }
static double toDefault(double value) { return value * Policy::factor(); } //!< convert from this unit to the default unit
static double fromDefault(double value) { return value / Policy::factor(); } //!< convert to this unit from the default unit
};
/*!
@@ -99,10 +84,10 @@ namespace BlackMisc
* \tparam Policy a policy class with static methods factor() and offset() returning double
*/
template <class Policy>
struct AffineConverter : public Converter
struct AffineConverter
{
virtual double toDefault(double value) const override { return (value - Policy::offset()) * Policy::factor(); }
virtual double fromDefault(double value) const override { return value / Policy::factor() + Policy::offset(); }
static double toDefault(double value) { return (value - Policy::offset()) * Policy::factor(); } //!< convert from this unit to the default unit
static double fromDefault(double value) { return value / Policy::factor() + Policy::offset(); } //!< convert to this unit from the default unit
};
/*!
@@ -111,16 +96,18 @@ namespace BlackMisc
* \tparam SubdivPolicy a policy class with static methods fraction() and subfactor() returning double
*/
template <class FactorPolicy, class SubdivPolicy>
struct SubdivisionConverter : public Converter
struct SubdivisionConverter
{
virtual double toDefault(double value) const override
//! convert from this unit to the default unit
static double toDefault(double value)
{
using BlackMisc::Math::CMathUtils;
double part2 = CMathUtils::fract(value) * SubdivPolicy::fraction();
value = CMathUtils::trunc(value) + part2 / SubdivPolicy::subfactor();
return value * FactorPolicy::factor();
}
virtual double fromDefault(double value) const override
//! convert to this unit from the default unit
static double fromDefault(double value)
{
using BlackMisc::Math::CMathUtils;
double part1 = CMathUtils::trunc(value / FactorPolicy::factor());
@@ -136,9 +123,10 @@ namespace BlackMisc
* \tparam SubdivPolicy a policy class with static methods fraction() and subfactor() returning double
*/
template <class FactorPolicy, class SubdivPolicy>
struct SubdivisionConverter2 : public Converter
struct SubdivisionConverter2
{
virtual double toDefault(double value) const override
//! convert from this unit to the default unit
static double toDefault(double value)
{
using BlackMisc::Math::CMathUtils;
double part2 = CMathUtils::fract(value) * SubdivPolicy::fraction();
@@ -146,7 +134,8 @@ namespace BlackMisc
value = CMathUtils::trunc(value) + (CMathUtils::trunc(part2) + part3 / SubdivPolicy::subfactor()) / SubdivPolicy::subfactor();
return value * FactorPolicy::factor();
}
virtual double fromDefault(double value) const override
//! convert to this unit from the default unit
static double fromDefault(double value)
{
using BlackMisc::Math::CMathUtils;
double part1 = CMathUtils::trunc(value / FactorPolicy::factor());
@@ -220,7 +209,8 @@ namespace BlackMisc
QString m_symbol; //!< unit name, e.g. "m"
double m_epsilon; //!< values with differences below epsilon are the equal
int m_displayDigits; //!< standard rounding for string conversions
QSharedDataPointer<Converter> m_converter; //!< strategy pattern allows an arbitrary conversion method as per object
ConverterFunction m_toDefault = nullptr; //!< convert from this unit to default unit
ConverterFunction m_fromDefault = nullptr; //!< convert to this unit from default unit
protected:
/*!
@@ -228,7 +218,7 @@ namespace BlackMisc
*/
template <class Converter>
CMeasurementUnit(const QString &name, const QString &symbol, const Converter &, int displayDigits, double epsilon)
: m_name(name), m_symbol(symbol), m_epsilon(epsilon), m_displayDigits(displayDigits), m_converter(new Converter)
: m_name(name), m_symbol(symbol), m_epsilon(epsilon), m_displayDigits(displayDigits), m_toDefault(Converter::toDefault), m_fromDefault(Converter::fromDefault)
{}
/*!
@@ -326,7 +316,7 @@ namespace BlackMisc
//! Is unit null?
bool isNull() const
{
return this->m_converter.data() == nullptr;
return this->m_toDefault == nullptr;
}
// --------------------------------------------------------------------