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package temperature
import (
"errors"
"fmt"
)
type unit int
const (
Celcius unit = iota
Kelvin
Fahrenheit
)
// UnitStrings returns a slice of strings, each representing a
// unit.
// This is necessary because giu.Combo only works with strings.
func UnitStrings() []string {
return []string{"°C", "°K", "°F"}
}
const (
DefaultUnit unit = Celcius
// DefaultUnitIndex is used to index UnitStrings().
DefaultUnitIndex int32 = 0 // celcius
)
func UnitFromString(s string) (unit, error) {
// Each case corresponds to a value in UnitStrings().
switch s {
case "°C":
return Celcius, nil
case "°K":
return Kelvin, nil
case "°F":
return Fahrenheit, nil
default:
return *new(unit), errors.New(fmt.Sprintf("invalid unit: '%s'", s))
}
}
type Temperature struct {
Val float32
Unit unit
}
func (t Temperature) AsUnit(u unit) (float32, error) {
// Convert to celcius
var c float32
switch t.Unit {
case Celcius:
c = t.Val
case Kelvin:
c = t.Val - 272.15
case Fahrenheit:
c = (t.Val - 32.0) * (5.0 / 9.0)
}
// Convert to desired unit
switch u {
case Celcius:
return c, nil
case Kelvin:
return c + 272.15, nil
case Fahrenheit:
return c*(9.0/5.0) + 32.0, nil
default:
return 0, errors.New(fmt.Sprintf("invalid unit: '%v'", u))
}
}
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