ex_go_clock/clock.go

// Package clock represents a dateless time of day.
package clock

import "fmt"

const (
	testVersion    = 3
	minutesPerHour = 60
	minutesPerDay  = 1440
)

// A Clock stores a minute value representing a time of day.
type Clock int

// String returns an hour:minute representation of the Clock.
func (c Clock) String() string {
	return fmt.Sprintf("%02d:%02d", c/minutesPerHour, c%minutesPerHour)
}

// Add returns a Clock adjusted by the number of minutes specified.
func (c Clock) Add(minutes int) Clock {
	return parseTime(0, int(c)+minutes)
}

// New returns a Clock constructed from the given hour and minute values.
func New(hour, minutes int) Clock {
	return parseTime(hour, minutes)
}

// parseTime computes the number of minutes that represent the time.
func parseTime(hour, minutes int) Clock {
	// Compute the total minutes, factoring away multiple day values.
	total := (hour*minutesPerHour + minutes) % minutesPerDay
	// If total minutes is negative, roll forward one day.
	if total < 0 {
		total += minutesPerDay
	}
	return Clock(total)
}

// Benchmark versus previous iteration:
//
// benchmark                    old ns/op     new ns/op     delta
// BenchmarkAddMinutes-12       45.7          29.7          -35.01%
// BenchmarkCreateClocks-12     52.1          33.9          -34.93%