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package main
import (
"errors"
"fmt"
)
type temperatureUnit int
const (
celcius temperatureUnit = iota
kelvin
fahrenheit
)
// temperatureUnitStrings returns a slice of strings, each representing a
// temperatureUnit.
// This is necessary because giu.Combo only works with strings.
func temperatureUnitStrings() []string {
return []string{"°C", "°K", "°F"}
}
const (
defaultTemperatureUnit temperatureUnit = celcius
// Used to index temperatureUnitStrings
defaultTemperatureUnitIndex int32 = 0 // celcius
)
func temperatureUnitFromString(s string) (temperatureUnit, error) {
// Each case corresponds to a value in volumeUnitStrings.
switch s {
case "°C":
return celcius, nil
case "°K":
return kelvin, nil
case "°F":
return fahrenheit, nil
default:
return *new(temperatureUnit), errors.New(fmt.Sprintf("invalid temperatureUnit: '%s'", s))
}
}
type temperature struct {
val float32
unit temperatureUnit
}
func (t temperature) asUnit(u temperatureUnit) (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 temperatureUnit: '%v'", u))
}
}
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