var (
	Bi   = UnitOptionQuantity("bits")
	Data = UnitOptionQuantity("bytes")

	Byte      = NewUnit("byte", "B", Data)
	KiloByte  = NewUnit("kilobyte", "KB", Data)
	MegaByte  = NewUnit("megabyte", "MB", Data)
	GigaByte  = NewUnit("gigabyte", "GB", Data)
	TeraByte  = NewUnit("terabyte", "TB", Data)
	PetaByte  = NewUnit("petabyte", "PB", Data)
	ExaByte   = NewUnit("exabyte", "", Data)
	ZettaByte = NewUnit("zettabyte", "", Data)
	YottaByte = NewUnit("yottabyte", "", Data)

	Kibibyte = NewUnit("kibibyte", "KiB", Data, IEC)
	Mebibyte = NewUnit("mebibyte", "MiB", Data, IEC)
	Gibibyte = NewUnit("gibibyte", "GiB", Data, IEC)
	Tebibyte = NewUnit("tebibyte", "TiB", Data, IEC)
	Pebibyte = NewUnit("pebibyte", "PiB", Data, IEC)
	Exbibyte = NewUnit("exbibyte", "EiB", Data, IEC)
	Zebibyte = NewUnit("zebibyte", "ZiB", Data, IEC)
	Yobibyte = NewUnit("yobibyte", "YiB", Data, IEC)

	Bit     = NewUnit("bit", "b", Bi)
	KiloBit = Kilo(Bit)
	MegaBit = Mega(Bit)
	GigaBit = Giga(Bit)
	TeraBit = Tera(Bit)
	PetaBit = Peta(Bit)
	ExaBit  = Exa(Bit)

	Nibble = NewUnit("nibble", "", Data)
)

var (
	Energy = UnitOptionQuantity("energy")

	// metric
	Joule      = NewUnit("joule", "J", Energy)
	KiloJoule  = Kilo(Joule)
	MegaJoule  = Mega(Joule)
	GigaJoule  = Giga(Joule)
	TeraJoule  = Tera(Joule)
	PetaJoule  = Peta(Joule)
	ExaJoule   = Exa(Joule)
	ZettaJoule = Zetta(Joule)
	YottaJoule = Yotta(Joule)
	MilliJoule = Milli(Joule)
	MicroJoule = Micro(Joule)
	NanoJoule  = Nano(Joule)
	PicoJoule  = Pico(Joule)
	FemtoJoule = Femto(Joule)
	AttoJoule  = Atto(Joule)

	WattHour     = NewUnit("watt-hour", "Wh", Energy)
	KiloWattHour = Kilo(WattHour)
	GigaWattHour = Giga(WattHour)
	MegaWattHour = Mega(WattHour)
	TeraWattHour = Tera(WattHour)
	PetaWattHour = Peta(WattHour)

	// other
	ElectronVolt = NewUnit("electronvolt", "eV", Energy)
	Calorie      = NewUnit("calorie", "cal", Energy)
)

var (
	Length = UnitOptionQuantity("length")

	// metric
	Meter      = NewUnit("meter", "m", Length, SI, UnitOptionAliases("metre"))
	ExaMeter   = Exa(Meter)
	PetaMeter  = Peta(Meter)
	TeraMeter  = Tera(Meter)
	GigaMeter  = Giga(Meter)
	MegaMeter  = Mega(Meter)
	KiloMeter  = Kilo(Meter)
	HectoMeter = Hecto(Meter)
	DecaMeter  = Deca(Meter)
	DeciMeter  = Deci(Meter)
	CentiMeter = Centi(Meter)
	MilliMeter = Milli(Meter)
	MicroMeter = Micro(Meter)
	NanoMeter  = Nano(Meter)
	PicoMeter  = Pico(Meter)
	FemtoMeter = Femto(Meter)
	AttoMeter  = Atto(Meter)

	Angstrom = NewUnit("angstrom", "Å", Length, BI, UnitOptionPlural("angstroms"))
	Inch     = NewUnit("inch", "in", Length, BI, UnitOptionPlural("inches"))
	Foot     = NewUnit("foot", "ft", Length, BI, UnitOptionPlural("feet"))
	Yard     = NewUnit("yard", "yd", Length, BI)
	Mile     = NewUnit("mile", "mi", Length, BI)
	League   = NewUnit("league", "lea", Length, BI)
	Furlong  = NewUnit("furlong", "fur", Length, BI)
)

var (
	Mass = UnitOptionQuantity("mass")

	// metric
	Gram      = NewUnit("gram", "g", Mass)
	ExaGram   = Exa(Gram)
	PetaGram  = Peta(Gram)
	TeraGram  = Tera(Gram)
	GigaGram  = Giga(Gram)
	MegaGram  = Mega(Gram)
	KiloGram  = Kilo(Gram)
	HectoGram = Hecto(Gram)
	DecaGram  = Deca(Gram)
	DeciGram  = Deci(Gram)
	CentiGram = Centi(Gram)
	MilliGram = Milli(Gram)
	MicroGram = Micro(Gram)
	NanoGram  = Nano(Gram)
	PicoGram  = Pico(Gram)
	FemtoGram = Femto(Gram)
	AttoGram  = Atto(Gram)

	// imperial
	Grain  = NewUnit("grain", "gr", Mass, BI)
	Drachm = NewUnit("drachm", "dr", Mass, BI)
	Ounce  = NewUnit("ounce", "oz", Mass, BI)
	Pound  = NewUnit("pound", "lb", Mass, BI)
	Stone  = NewUnit("stone", "st", Mass, BI)
	Ton    = NewUnit("ton", "t", Mass, BI)
	Slug   = NewUnit("slug", "", Mass, BI)
)

var (
	Power = UnitOptionQuantity("power")

	// metric
	Watt      = NewUnit("watt", "W", Power)
	KiloWatt  = Kilo(Watt)
	MegaWatt  = Mega(Watt)
	GigaWatt  = Giga(Watt)
	TeraWatt  = Tera(Watt)
	PetaWatt  = Peta(Watt)
	ExaWatt   = Exa(Watt)
	ZettaWatt = Zetta(Watt)
	YottaWatt = Yotta(Watt)
)

var (
	Pressure = UnitOptionQuantity("pressure")

	// SI unit metric
	Pascal      = NewUnit("pascal", "Pa", Pressure, SI)
	ExaPascal   = Exa(Pascal)
	PetaPascal  = Peta(Pascal)
	TeraPascal  = Tera(Pascal)
	GigaPascal  = Giga(Pascal)
	MegaPascal  = Mega(Pascal)
	KiloPascal  = Kilo(Pascal)
	HectoPascal = Hecto(Pascal)
	DecaPascal  = Deca(Pascal)
	DeciPascal  = Deci(Pascal)
	CentiPascal = Centi(Pascal)
	MilliPascal = Milli(Pascal)
	MicroPascal = Micro(Pascal)
	NanoPascal  = Nano(Pascal)
	PicoPascal  = Pico(Pascal)
	FemtoPascal = Femto(Pascal)
	AttoPascal  = Atto(Pascal)

	// Other
	At       = NewUnit("technical atmosphere", "at", Pressure, BI, UnitOptionPlural("technical atmospheres"))
	Atm      = NewUnit("standard atmosphere", "atm", Pressure, BI, UnitOptionPlural("standard atmospheres"))
	Bar      = NewUnit("bar", "bar", Pressure, BI, UnitOptionPlural("bars"))
	CentiBar = Centi(Bar)
	MilliBar = Milli(Bar)
	MicroBar = Micro(Bar)
	Barye    = NewUnit("barye", "Ba", Pressure, BI, UnitOptionPlural("baryes"))
	InH2O    = NewUnit("inch of Water Column", "inH2O", Pressure, BI)
	InHg     = NewUnit("inch of Mercury", "inHg", Pressure, BI)
	MH2O     = NewUnit("meter of Water Column", "mmH2O", Pressure, BI, UnitOptionPlural("meters of Water Column"))
	MmH2O    = Milli(MH2O)
	CmH2O    = Centi(MH2O)
	MHg      = NewUnit("meter of Mercury", "mmHg", Pressure, BI, UnitOptionPlural("meters of Mercury"))
	MmHg     = Milli(MHg)
	CmHg     = Centi(MHg)
	Newton   = NewUnit("newton per square meter", "N/m²", Pressure, BI)
	Psi      = NewUnit("pound-force per square inch", "psi", Pressure, BI)
	Torr     = NewUnit("torr", "Torr", Pressure, BI)
)

var (
	Temp = UnitOptionQuantity("temperature")

	Celsius    = NewUnit("celsius", "C", Temp, UnitOptionPlural("none"), SI)
	Fahrenheit = NewUnit("fahrenheit", "F", Temp, UnitOptionPlural("none"), US)
	Kelvin     = NewUnit("kelvin", "K", Temp, UnitOptionPlural("none"), SI)
)

var (
	Time = UnitOptionQuantity("time")

	Second      = NewUnit("second", "s", Time)
	ExaSecond   = Exa(Second)
	PetaSecond  = Peta(Second)
	TeraSecond  = Tera(Second)
	GigaSecond  = Giga(Second)
	MegaSecond  = Mega(Second)
	KiloSecond  = Kilo(Second)
	HectoSecond = Hecto(Second)
	DecaSecond  = Deca(Second)
	DeciSecond  = Deci(Second)
	CentiSecond = Centi(Second)
	MilliSecond = Milli(Second)
	MicroSecond = Micro(Second)
	NanoSecond  = Nano(Second)
	PicoSecond  = Pico(Second)
	FemtoSecond = Femto(Second)
	AttoSecond  = Atto(Second)

	Minute = NewUnit("minute", "min", Time)
	Hour   = NewUnit("hour", "hr", Time)
	Day    = NewUnit("day", "d", Time)
	Month  = NewUnit("month", "", Time)
	Year   = NewUnit("year", "yr", Time)

	Decade     = NewUnit("decade", "", Time)
	Century    = NewUnit("century", "", Time)
	Millennium = NewUnit("millennium", "", Time)

	// more esoteric time units
	PlanckTime = NewUnit("planck time", "𝑡ₚ", Time)
	Fortnight  = NewUnit("fortnight", "", Time)
	Score      = NewUnit("score", "", Time)
)

var (
	// Shorthand for pre-defined unit systems
	BI  = UnitOptionSystem("imperial")
	SI  = UnitOptionSystem("metric")
	US  = UnitOptionSystem("us")
	IEC = UnitOptionSystem("iec")
)

var (
	Volume = UnitOptionQuantity("volume")

	// metric
	Liter      = NewUnit("liter", "l", Volume, SI, UnitOptionAliases("litre"))
	ExaLiter   = Exa(Liter)
	PetaLiter  = Peta(Liter)
	TeraLiter  = Tera(Liter)
	GigaLiter  = Giga(Liter)
	MegaLiter  = Mega(Liter)
	KiloLiter  = Kilo(Liter)
	HectoLiter = Hecto(Liter)
	DecaLiter  = Deca(Liter)
	DeciLiter  = Deci(Liter)
	CentiLiter = Centi(Liter)
	MilliLiter = Milli(Liter)
	MicroLiter = Micro(Liter)
	NanoLiter  = Nano(Liter)
	PicoLiter  = Pico(Liter)
	FemtoLiter = Femto(Liter)
	AttoLiter  = Atto(Liter)

	// imperial
	Quart      = NewUnit("quart", "qt", Volume, BI)
	Pint       = NewUnit("pint", "pt", Volume, BI)
	Gallon     = NewUnit("gallon", "gal", Volume, BI)
	FluidOunce = NewUnit("fluid ounce", "fl oz", Volume, BI, UnitOptionAliases("floz"))

	// US
	FluidQuart          = NewUnit("fluid quart", "fl qt", Volume, US)
	FluidPint           = NewUnit("fluid pint", "fl pt", Volume, US)
	FluidGallon         = NewUnit("fluid gallon", "", Volume, US)
	CustomaryFluidOunce = NewUnit("customary fluid ounce", "", Volume, US)
)

var DefaultFmtOptions = FmtOptions{true, false, 6}

type Conversion struct {
	Fn      ConversionFn
	Formula string
	// contains filtered or unexported fields
}

type ConversionFn func(float64) float64

type FmtOptions struct {
	Label     bool // if false, unit label/symbol will be omitted
	Short     bool // if true, use unit shortname or symbol
	Precision int  // maximum meaningful precision to truncate value
}

type Unit struct {
	Name     string
	Symbol   string
	Quantity string
	// contains filtered or unexported fields
}

type UnitList []Unit

type UnitOption func(Unit) Unit

type Value struct {
	// contains filtered or unexported fields
}