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package pressure
import (
"errors"
"fmt"
)
type unit float32
const (
Pascal unit = 1
Kilopascal unit = 1_000
Bar unit = 100_000
PoundsPerSquareInch unit = 6_894.757
)
// 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{"Pa", "kPa", "bar", "psi"}
}
const (
DefaultUnit unit = Kilopascal
// DefaultUnitIndex is used to index UnitStrings().
DefaultUnitIndex int32 = 1 // kPa
)
func UnitFromString(s string) (unit, error) {
// Each case corresponds to a value in UnitStrings().
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(unit), errors.New(fmt.Sprintf("invalid unit: '%s'", s))
}
}
type Pressure struct {
Val float32
Unit unit
}
func (p Pressure) AsUnit(u unit) float32 {
pa := p.Val * float32(p.Unit) // Convert to pascals.
return pa / float32(u) // Convert to desired unit.
}
func Atmospheric() Pressure {
return Pressure{1, Bar}
}
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