Add convert rules. (1ee2a5bb) · Commits · Kevin Lyda / units

rules/rules.go

+46 −3

Original line number	Diff line number	Diff line
		@@ -3,6 +3,7 @@ package rules

		import (
		"errors"
		"fmt"

		"github.com/ichiban/prolog"
		)
		@@ -14,6 +15,9 @@ type Engine struct {

		var (
		prologKinds = `
		unit_kind(f, temperature).
		unit_kind(k, temperature).
		unit_kind(c, temperature).
		unit_kind(m2, area).
		unit_kind(cm2, area).
		unit_kind(cm, distance).
		@@ -28,9 +32,22 @@ var (
		unit_kind(butter, density).
		unit_kind(water, density).
		`
		prologKindsConvert = `
		convert_kind(mass, volume, density).
		convert_kind(volume, area, distance).
		prologConvert = `
		rule(GivenQuant, f, TargetQuant, c) :-
		TargetQuant is (GivenQuant - 32) * 5 / 9.
		rule(GivenQuant, c, TargetQuant, f) :-
		TargetQuant is (GivenQuant / 5 * 9) + 32.
		rule(GivenQuant, c, TargetQuant, k) :-
		TargetQuant is GivenQuant + 273.15.
		rule(GivenQuant, k, TargetQuant, c) :-
		TargetQuant is GivenQuant - 273.15.
		rule(GivenQuant, GivenUnit, TargetQuant, TargetUnit) :-
		rule(GivenQuant, GivenUnit, X, Y),
		rule(X, Y, TargetQuant, TargetUnit).
		convert(GivenQuant, GivenUnit, TargetQuant, TargetUnit) :-
		unit_kind(GivenUnit, temperature),
		unit_kind(TargetUnit, temperature),
		rule(GivenQuant, GivenUnit, TargetQuant, TargetUnit).
		`
		)

		@@ -48,6 +65,10 @@ func New() (*Engine, error) {
		return nil, err
		}

		if err := ngn.p.Exec(prologConvert); err != nil {
		return nil, err
		}

		return ngn, nil
		}

		@@ -74,3 +95,25 @@ func (ngn *Engine) Kind(unit string) (string, error) {
		}
		return result, nil
		}

		// Convert converts units.
		func (ngn *Engine) Convert(qty float64, givenUnit, targetUnit string) (float64, error) {
		sols, err := ngn.p.Query("convert(?, ?, Qty, ?).", qty, givenUnit, targetUnit)
		if err != nil {
		fmt.Println("Huh?")
		return 0, err
		}
		defer sols.Close()

		for sols.Next() {
		var quantity struct {
		Qty float64
		}
		if err := sols.Scan(&quantity); err != nil {
		fmt.Println("Scan?")
		return 0, err
		}
		return quantity.Qty, err
		}
		return 0, err
		}

rules/rules_test.go

+29 −0

Original line number	Diff line number	Diff line
		@@ -30,3 +30,32 @@ func TestKinds(t *testing.T) {
		})
		}
		}

		func TestConverts(t *testing.T) {
		cases := []struct {
		name string
		qty float64
		given string
		target string
		result float64
		}{
		{
		"c to f",
		22.0,
		"c",
		"f",
		71.6,
		},
		}

		ngn, err := New()
		assert.NoError(t, err)
		for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
		result, err := ngn.Convert(tc.qty, tc.given, tc.target)
		assert.NoError(t, err)

		assert.InDelta(t, tc.result, result, 0.1)
		})
		}
		}