mass flow rate

1 files changed, 86 insertions, 0 deletions

diff --git a/mass.go b/mass.go
new file mode 100644
index 0000000..0b97020
--- /dev/null
+++ b/mass.go
@@ -0,0 +1,86 @@
+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.
+}