number: added number package

provides more styles and more control over
formatting than fmt.

Change-Id: Ib9d2c27db14804af911556e3caa8b35fddd32fce
Reviewed-on: https://go-review.googlesource.com/59812
Run-TryBot: Marcel van Lohuizen <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Nigel Tao <[email protected]>

number/doc.go

@@ -0,0 +1,29 @@
+// Copyright 2017 The Go 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 number formats numbers according to the customs of different locales.
+//
+// The number formats of this package allow for greater formatting flexibility
+// than passing values to message.Printf calls as is. It currently supports the
+// builtin Go types and anything that implements the Convert interface
+// (currently internal).
+//
+//    p := message.NewPrinter(language.English)
+//
+//    p.Printf("%v bottles of beer on the wall.", number.Decimal(1234))
+//    // Prints: 1,234 bottles of beer on the wall.
+//
+//    p.Printf("%v of gophers lose too much fur", number.Percent(0.12))
+//    // Prints: 12% of gophers lose too much fur.
+//
+//    p := message.NewPrinter(language.Dutch)
+//
+//    p.Printf("There are %v bikes per household.", number.Decimal(1.2))
+//    // Prints: Er zijn 1,2 fietsen per huishouden.
+//
+// Provided that the printed translation is available.
+//
+// The width and scale specified in the formatting directives override the
+// configuration of the formatter.
+package number

number/examples_test.go

@@ -0,0 +1,28 @@
+// Copyright 2017 The Go 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 number_test
+
+import (
+	"golang.org/x/text/language"
+	"golang.org/x/text/message"
+	"golang.org/x/text/number"
+)
+
+func ExampleMaxIntegerDigits() {
+	const year = 1999
+	p := message.NewPrinter(language.English)
+	p.Println("Year:", number.Decimal(year, number.MaxIntegerDigits(2)))
+
+	// Output:
+	// Year: 99
+}
+
+func ExampleIncrementString() {
+	p := message.NewPrinter(language.English)
+
+	p.Println(number.Decimal(1.33, number.IncrementString("0.50")))
+
+	// Output: 1.50
+}

number/format.go

@@ -0,0 +1,106 @@
+// Copyright 2017 The Go 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 number
+
+import (
+	"fmt"
+	"strings"
+
+	"golang.org/x/text/feature/plural"
+	"golang.org/x/text/internal/format"
+	"golang.org/x/text/internal/number"
+	"golang.org/x/text/language"
+)
+
+// A FormatFunc formates a number.
+type FormatFunc func(x interface{}, opts ...Option) Formatter
+
+// NewFormat creates a FormatFunc based on another FormatFunc and new options.
+// Use NewFormat to cash the creation of formatters.
+func NewFormat(format FormatFunc, opts ...Option) FormatFunc {
+	o := *format(nil).options
+	n := len(o.options)
+	o.options = append(o.options[:n:n], opts...)
+	return func(x interface{}, opts ...Option) Formatter {
+		return newFormatter(&o, opts, x)
+	}
+}
+
+type options struct {
+	verbs      string
+	initFunc   initFunc
+	options    []Option
+	pluralFunc func(t language.Tag, scale int) (f plural.Form, n int)
+}
+
+type optionFlag uint16
+
+const (
+	hasScale optionFlag = 1 << iota
+	hasPrecision
+	noSeparator
+	exact
+)
+
+type initFunc func(f *number.Formatter, t language.Tag)
+
+func newFormatter(o *options, opts []Option, value interface{}) Formatter {
+	if len(opts) > 0 {
+		n := *o
+		n.options = opts
+		o = &n
+	}
+	return Formatter{o, value}
+}
+
+func newOptions(verbs string, f initFunc) *options {
+	return &options{verbs: verbs, initFunc: f}
+}
+
+type Formatter struct {
+	*options
+	value interface{}
+}
+
+// Format implements format.Formatter. It is for internal use only for now.
+func (f Formatter) Format(state format.State, verb rune) {
+	// TODO: consider implementing fmt.Formatter instead and using the following
+	// piece of code. This allows numbers to be rendered mostly as expected
+	// when using fmt. But it may get weird with the spellout options and we
+	// may need more of format.State over time.
+	// lang := language.Und
+	// if s, ok := state.(format.State); ok {
+	// 	lang = s.Language()
+	// }
+
+	lang := state.Language()
+	if !strings.Contains(f.verbs, string(verb)) {
+		fmt.Fprintf(state, "%%!%s(%T=%v)", string(verb), f.value, f.value)
+		return
+	}
+	var p number.Formatter
+	f.initFunc(&p, lang)
+	for _, o := range f.options.options {
+		o(lang, &p)
+	}
+	if w, ok := state.Width(); ok {
+		p.FormatWidth = uint16(w)
+	}
+	if prec, ok := state.Precision(); ok {
+		switch verb {
+		case 'd':
+			p.SetScale(0)
+		case 'f':
+			p.SetScale(prec)
+		case 'e':
+			p.SetPrecision(prec + 1)
+		case 'g':
+			p.SetPrecision(prec)
+		}
+	}
+	var d number.Decimal
+	d.Convert(p.RoundingContext, f.value)
+	state.Write(p.Format(nil, &d))
+}

number/format_test.go

@@ -0,0 +1,45 @@
+// Copyright 2017 The Go 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 number
+
+import (
+	"testing"
+
+	"golang.org/x/text/language"
+	"golang.org/x/text/message"
+)
+
+func TestWrongVerb(t *testing.T) {
+	testCases := []struct {
+		f    Formatter
+		fmt  string
+		want string
+	}{{
+		f:    Decimal(12),
+		fmt:  "%e",
+		want: "%!e(int=12)",
+	}, {
+		f:    Scientific(12),
+		fmt:  "%f",
+		want: "%!f(int=12)",
+	}, {
+		f:    Engineering(12),
+		fmt:  "%f",
+		want: "%!f(int=12)",
+	}, {
+		f:    Percent(12),
+		fmt:  "%e",
+		want: "%!e(int=12)",
+	}}
+	for _, tc := range testCases {
+		t.Run("", func(t *testing.T) {
+			tag := language.Und
+			got := message.NewPrinter(tag).Sprintf(tc.fmt, tc.f)
+			if got != tc.want {
+				t.Errorf("got %q; want %q", got, tc.want)
+			}
+		})
+	}
+}

number/number.go

@@ -0,0 +1,77 @@
+// Copyright 2017 The Go 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 number
+
+// TODO:
+//    p.Printf("The gauge was at %v.", number.Spell(number.Percent(23)))
+//    // Prints: The gauge was at twenty-three percent.
+//
+//    p.Printf("From here to %v!", number.Spell(math.Inf()))
+//    // Prints: From here to infinity!
+//
+
+import (
+	"golang.org/x/text/internal/number"
+)
+
+const (
+	decimalVerbs    = "vfgd"
+	scientificVerbs = "veg"
+)
+
+// Decimal represents a number as a floating point decimal.
+func Decimal(x interface{}, opts ...Option) Formatter {
+	return newFormatter(decimalOptions, opts, x)
+}
+
+var decimalOptions = newOptions(decimalVerbs, (*number.Formatter).InitDecimal)
+
+// Scientific prints a values in scientific format.
+func Scientific(x interface{}, opts ...Option) Formatter {
+	return newFormatter(scientificOptions, opts, x)
+}
+
+var scientificOptions = newOptions(scientificVerbs, (*number.Formatter).InitScientific)
+
+// Engineering formats a number using engineering notation, which is like
+// scientific notation, but with the exponent normalized to multiples of 3.
+func Engineering(x interface{}, opts ...Option) Formatter {
+	return newFormatter(engineeringOptions, opts, x)
+}
+
+var engineeringOptions = newOptions(scientificVerbs, (*number.Formatter).InitEngineering)
+
+// Percent formats a number as a percentage. A value of 1.0 means 100%.
+func Percent(x interface{}, opts ...Option) Formatter {
+	return newFormatter(percentOptions, opts, x)
+}
+
+var percentOptions = newOptions(decimalVerbs, (*number.Formatter).InitPercent)
+
+// PerMille formats a number as a per mille indication. A value of 1.0 means
+// 1000‰.
+func PerMille(x interface{}, opts ...Option) Formatter {
+	return newFormatter(perMilleOptions, opts, x)
+}
+
+var perMilleOptions = newOptions(decimalVerbs, (*number.Formatter).InitPerMille)
+
+// TODO:
+// - Shortest: akin to verb 'g' of 'G'
+//
+// TODO: RBNF forms:
+// - Compact: 1M 3.5T
+// - CompactBinary: 1Mi 3.5Ti
+// - Long: 1 million
+// - Ordinal:
+// - Roman: MCMIIXX
+// - RomanSmall: mcmiixx
+// - Text: numbers as it typically appears in running text, allowing
+//   language-specific choices for when to use numbers and when to use words.
+// - Spell?: spelled-out number. Maybe just allow as an option?
+
+// NOTE: both spelled-out numbers and ordinals, to render correctly, need
+// detailed linguistic information from the translated string into which they
+// are substituted. We will need to implement that first.