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package main
import (
"errors"
"fmt"
)
type pressureUnit float32
const (
pascal pressureUnit = 1
kilopascal pressureUnit = 1_000
bar pressureUnit = 100_000
poundsPerSquareInch pressureUnit = 6_894.757
)
// pressureUnitStrings returns a slice of strings, each representing a
// pressureUnit.
// This is necessary because giu.Combo only works with strings.
func pressureUnitStrings() []string {
return []string{"Pa", "kPa", "bar", "psi"}
}
const (
defaultPressureUnit pressureUnit = kilopascal
// Used to index pressureUnitStrings
defaultPressureUnitIndex int32 = 1 // kPa
)
func pressureUnitFromString(s string) (pressureUnit, error) {
// Each case corresponds to a value in pressureUnitStrings
switch s {
case "Pa":
return pascal, nil
case "kPa":
return kilopascal, nil
case "bar":
return bar, nil
case "psi":
return poundsPerSquareInch, nil
default:
return *new(pressureUnit), errors.New(fmt.Sprintf("invalid pressureUnit: '%s'", s))
}
}
type pressure struct {
val float32
unit pressureUnit
}
func newPressure() pressure {
return pressure{100, defaultPressureUnit}
}
func (p pressure) asUnit(u pressureUnit) float32 {
pa := p.val * float32(p.unit) // Convert to pascals.
return pa / float32(u) // Convert to desired unit.
}
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