code review 5543047: math/big: add examples for Rat and Int's SetString and ...

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

[adg, 2012-01-12 22:47:33]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://go.googlecode.com/hg

[bradfitz, 2012-01-12 22:49:03]

LGTM

On Thu, Jan 12, 2012 at 2:47 PM, <adg@golang.org> wrote:

> Reviewers: golang-dev_googlegroups.com,
>
> Message:
> Hello golang-dev@googlegroups.com,
>
> I'd like you to review this change to
> https://go.googlecode.com/hg
>
>
> Description:
> math/big: add examples for Int's SetString and Scan methods
>
> Please review this at
http://codereview.appspot.com/**5543047/<http://codereview.appspot.com/5543047/>
>
> Affected files:
>  A src/pkg/math/big/example_test.**go
>
>
> Index: src/pkg/math/big/example_test.**go
> ==============================**==============================**=======
> new file mode 100644
> --- /dev/null
> +++ b/src/pkg/math/big/example_**test.go
> @@ -0,0 +1,26 @@
> +// 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 (
> +       "math/big"
> +       "fmt"
> +)
> +
> +// 692875643197834568615209724987**62589673589754982742 <nil>
> +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("**692875643197834568615209724987**62589673589754982742",
> i)
> +       fmt.Println(i, err)
> +}
> +
> +// 232455871919350069994520617996**7386
> +func ExampleInt_SetString() {
> +       i := new(big.Int)
> +       i.SetString("**712340345050202340560350352054**2030632", 8) //
> octal
> +       fmt.Println(i)
> +}
>
>
>

[rsc, 2012-01-12 22:50:00]

Why use such ridiculous numbers?

[adg, 2012-01-12 23:01:45]

On 13 January 2012 09:50, Russ Cox <rsc@golang.org> wrote:
> Why use such ridiculous numbers?

Happy to use different ones. Got any suggestions?

[r2, 2012-01-12 23:02:40]

On Jan 12, 2012, at 3:01 PM, Andrew Gerrand wrote:

> On 13 January 2012 09:50, Russ Cox <rsc@golang.org> wrote:
>> Why use such ridiculous numbers?
> 
> Happy to use different ones. Got any suggestions?

12
123
1234
12345

[adg, 2012-01-12 23:04:26]

Hello golang-dev@googlegroups.com, bradfitz@golang.org, rsc@golang.org,
r@google.com (cc: golang-dev@googlegroups.com),

Please take another look.

[adg, 2012-01-12 23:05:57]

Also added an example for Rat.

[gri, 2012-01-12 23:09:09]

http://codereview.appspot.com/5543047/diff/4003/src/pkg/math/big/example_test.go
File src/pkg/math/big/example_test.go (right):

http://codereview.appspot.com/5543047/diff/4003/src/pkg/math/big/example_test...
src/pkg/math/big/example_test.go:14: // Calculate the square root of x using
Newton's method.
I don't think this is a good example because at the end you get a
small-precision float. Why not use float32?

This should be an example where rational numbers matter.

[adg, 2012-01-24 05:33:59]

Hello golang-dev@googlegroups.com, bradfitz@golang.org, rsc@golang.org,
r@google.com, gri@golang.org (cc: golang-dev@googlegroups.com),

Please take another look.

[r, 2012-01-24 15:44:17]

LGTM but wait for others

http://codereview.appspot.com/5543047/diff/8001/src/pkg/math/big/example_test.go
File src/pkg/math/big/example_test.go (right):

http://codereview.appspot.com/5543047/diff/8001/src/pkg/math/big/example_test...
src/pkg/math/big/example_test.go:32: fmt.Println(r, err)
use idiomatic code

if err == nil {
  fmt.Println("error scanning value:", err)
} else {
  fmt.Println(r)
}

http://codereview.appspot.com/5543047/diff/8001/src/pkg/math/big/example_test...
src/pkg/math/big/example_test.go:41: fmt.Println(i, err)
ditto

[gri, 2012-01-24 17:33:16]

LGTM

http://codereview.appspot.com/5543047/diff/8001/src/pkg/math/big/example_test.go
File src/pkg/math/big/example_test.go (right):

http://codereview.appspot.com/5543047/diff/8001/src/pkg/math/big/example_test...
src/pkg/math/big/example_test.go:31: _, err := fmt.Sscan("1.5000", r)
make this 3.142 and then the printed fraction should be 355/113 like above. more
interesting than 1.5

[adg, 2012-01-24 23:29:55]

*** Submitted as http://code.google.com/p/go/source/detail?r=60013c96035b ***

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

R=golang-dev, bradfitz, rsc, r, gri, r
CC=golang-dev
http://codereview.appspot.com/5543047

http://codereview.appspot.com/5543047/diff/8001/src/pkg/math/big/example_test.go
File src/pkg/math/big/example_test.go (right):

http://codereview.appspot.com/5543047/diff/8001/src/pkg/math/big/example_test...
src/pkg/math/big/example_test.go:31: _, err := fmt.Sscan("1.5000", r)
On 2012/01/24 17:33:17, gri wrote:
> make this 3.142 and then the printed fraction should be 355/113 like above.
more
> interesting than 1.5

355/133 isn't exactly 3.142, so that won't work.

http://codereview.appspot.com/5543047/diff/8001/src/pkg/math/big/example_test...
src/pkg/math/big/example_test.go:32: fmt.Println(r, err)
On 2012/01/24 15:44:18, r wrote:
> use idiomatic code
> 
> if err == nil {
>   fmt.Println("error scanning value:", err)
> } else {
>   fmt.Println(r)
> }

Done.

http://codereview.appspot.com/5543047/diff/8001/src/pkg/math/big/example_test...
src/pkg/math/big/example_test.go:41: fmt.Println(i, err)
On 2012/01/24 15:44:18, r wrote:
> ditto

Done.