text/tabwriter: fix documentation by adding an example.

R=rsc, r
CC=golang-dev
https://golang.org/cl/5685069

src/pkg/text/tabwriter/example_test.go

+// Copyright 2012 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 tabwriter_test
+
+import (
+	"fmt"
+	"os"
+	"text/tabwriter"
+)
+
+func ExampleWriter_Init() {
+	w := new(tabwriter.Writer)
+
+	// Format in tab-separated columns with a tab stop of 8.
+	w.Init(os.Stdout, 0, 8, 0, '\t', 0)
+	fmt.Fprintln(w, "a\tb\tc\td\t.")
+	fmt.Fprintln(w, "123\t12345\t1234567\t123456789\t.")
+	fmt.Fprintln(w)
+	w.Flush()
+
+	// Format right-aligned in space-separated columns of minimal width 5
+	// and at least one blank of padding (so wider column entries do not
+	// touch each other).
+	w.Init(os.Stdout, 5, 0, 1, ' ', tabwriter.AlignRight)
+	fmt.Fprintln(w, "a\tb\tc\td\t.")
+	fmt.Fprintln(w, "123\t12345\t1234567\t123456789\t.")
+	fmt.Fprintln(w)
+	w.Flush()
+
+	// output:
+	// a	b	c	d		.
+	// 123	12345	1234567	123456789	.
+	//
+	//     a     b       c         d.
+	//   123 12345 1234567 123456789.
+}

src/pkg/text/tabwriter/tabwriter.go

@@ -169,12 +169,6 @@ const (
 //			to the tab width in the viewer displaying the result)
 //	flags		formatting control
 //
-// To format in tab-separated columns with a tab stop of 8:
-//	b.Init(w, 8, 1, 8, '\t', 0);
-//
-// To format in space-separated columns with at least 4 spaces between columns:
-//	b.Init(w, 0, 4, 8, ' ', 0);
-//
 func (b *Writer) Init(output io.Writer, minwidth, tabwidth, padding int, padchar byte, flags uint) *Writer {
 	if minwidth < 0 || tabwidth < 0 || padding < 0 {
 		panic("negative minwidth, tabwidth, or padding")