math/big: add examples for Rat and Int's SetString and Scan methods

R=golang-dev, bradfitz, rsc, r, gri, r
CC=golang-dev
https://golang.org/cl/5543047

diff --git a/src/pkg/math/big/example_test.go b/src/pkg/math/big/example_test.go
new file mode 100644 (file)
index 0000000..ba676ec
--- /dev/null
+++ b/src/pkg/math/big/example_test.go
@@ -0,0 +1,51 @@
+// 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 big_test
+
+import (
+       "fmt"
+       "log"
+       "math/big"
+)
+
+// 3.142
+func ExampleRat_SetString() {
+       r := new(big.Rat)
+       r.SetString("355/113")
+       fmt.Println(r.FloatString(3))
+}
+
+// 420
+func ExampleInt_SetString() {
+       i := new(big.Int)
+       i.SetString("644", 8) // octal
+       fmt.Println(i)
+}
+
+// 3/2
+func ExampleRat_Scan() {
+       // The Scan function is rarely used directly;
+       // the fmt package recognizes it as an implementation of fmt.Scanner.
+       r := new(big.Rat)
+       _, err := fmt.Sscan("1.5000", r)
+       if err != nil {
+               log.Println("error scanning value:", err)
+       } else {
+               fmt.Println(r)
+       }
+}
+
+// 18446744073709551617
+func ExampleInt_Scan() {
+       // The Scan function is rarely used directly;
+       // the fmt package recognizes it as an implementation of fmt.Scanner.
+       i := new(big.Int)
+       _, err := fmt.Sscan("18446744073709551617", i)
+       if err != nil {
+               log.Println("error scanning value:", err)
+       } else {
+               fmt.Println(i)
+       }
+}