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package main
import (
"errors"
"fmt"
"time"
)
type massUnit float32
const (
gram massUnit = 1
kilogram massUnit = 1_000
pound massUnit = 453.5924
)
type mass struct {
val float32
unit massUnit
}
func (m mass) asUnit(u massUnit) float32 {
g := m.val * float32(m.unit) // Convert to grams.
return g / float32(u) // Convert to desired unit.
}
type massFlowRateUnit float32
const (
kilogramsPerSecond massFlowRateUnit = 1
poundsPerMinute massFlowRateUnit = 0.007_559_872_833
)
// massFlowRateUnitStrings returns a slice of strings, each representing a
// massFlowRateUnit.
// This is necessary because giu.Combo only works with strings.
func massFlowRateUnitStrings() []string {
return []string{"kg/s", "lb/min"}
}
const (
defaultMassFlowRateUnit massFlowRateUnit = kilogramsPerSecond
//Used to index massFlowRateUnitStrings
defaultMassFlowRateUnitIndex int32 = 0 // kg/s
)
func massFlowRateUnitFromString(s string) (massFlowRateUnit, error) {
// Each case corresponds to a value in massFlowRateUnitStrings.
switch s {
case "kg/s":
return kilogramsPerSecond, nil
case "lb/min":
return poundsPerMinute, nil
default:
return *new(massFlowRateUnit), errors.New(
fmt.Sprintf("invalid massFlowRateUnit: '%s'", s))
}
}
type massFlowRate struct {
val float32
unit massFlowRateUnit
}
func newMassFlowRate(m mass, t time.Duration, u massFlowRateUnit) (massFlowRate, error) {
switch u {
case kilogramsPerSecond:
return massFlowRate{
m.asUnit(kilogram) / float32(t.Seconds()),
u,
}, nil
case poundsPerMinute:
return massFlowRate{
m.asUnit(pound) / float32(t.Minutes()),
u,
}, nil
default:
return *new(massFlowRate), errors.New(
fmt.Sprintf("invalid massFlowRateUnit: '%v'", u))
}
}
func (fr massFlowRate) asUnit(u massFlowRateUnit) float32 {
kgps := fr.val * float32(fr.unit) // Convert to kilogramsPerSecond.
return kgps / float32(u) // Convert to desired unit.
}
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