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package main
import (
"errors"
"fmt"
)
type volumeUnit float32
const (
cubicCentimetre volumeUnit = 1
litre volumeUnit = 1_000
cubicMetre volumeUnit = 1_000_000
cubicInch volumeUnit = 16.38706
)
// volumeUnitStrings returns a slice of strings, each representing a
// volumeUnit.
// This is necessary because giu.Combo only works with strings.
func volumeUnitStrings() []string {
return []string{"cc", "L", "m³", "in³"}
}
const (
defaultVolumeUnit volumeUnit = cubicCentimetre
// Used to index volumeUnitStrings
defaultVolumeUnitIndex int32 = 0 // cc
)
func volumeUnitFromString(s string) (volumeUnit, error) {
// Each case corresponds to a value in volumeUnitStrings
switch s {
case "cc":
return cubicCentimetre, nil
case "L":
return litre, nil
case "m³":
return cubicMetre, nil
case "in³":
return cubicInch, nil
default:
return *new(volumeUnit), errors.New(fmt.Sprintf("invalid volumeUnit: '%s'", s))
}
}
type volume struct {
val float32
unit volumeUnit
}
func (v volume) asUnit(u volumeUnit) float32 {
cc := v.val * float32(v.unit) // Convert to cubic centimetres.
return cc / float32(u) // Convert to desired unit.
}
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