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// Copyright ©2013 The gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package unit
import (
// Dimless represents a dimensionless constant
type Dimless float64
const (
One Dimless = 1.0
// Unit converts the Dimless to a unit
func (d Dimless) Unit() *Unit {
return New(float64(d), Dimensions{})
// Dimless allows Dimless to implement a Dimlesser interface
func (d Dimless) Dimless() Dimless {
return d
// From converts the unit to a dimless. Returns an error if there
// is a mismatch in dimension
func (d *Dimless) From(u *Unit) error {
if !DimensionsMatch(u, One) {
(*d) = Dimless(math.NaN())
return errors.New("Dimension mismatch")
(*d) = Dimless(u.Unit().Value())
return nil
func (d Dimless) Format(fs fmt.State, c rune) {
switch c {
case 'v':
if fs.Flag('#') {
fmt.Fprintf(fs, "%T(%v)", d, float64(d))
case 'e', 'E', 'f', 'F', 'g', 'G':
p, pOk := fs.Precision()
w, wOk := fs.Width()
switch {
case pOk && wOk:
fmt.Fprintf(fs, "%*.*"+string(c), w, p, float64(d))
case pOk:
fmt.Fprintf(fs, "%.*"+string(c), p, float64(d))
case wOk:
fmt.Fprintf(fs, "%*"+string(c), w, float64(d))
fmt.Fprintf(fs, "%"+string(c), float64(d))
fmt.Fprintf(fs, "%%!%c(%T=%g)", c, d, float64(d))