Why no rand.Uint64()?

[Aaron Jacobs]

The math/rand package seems to be built around uniformly-distributed random
integers in [0, 2^63), with the fundamental building block being Source's
Int63() method. Even Rand has no Uint64() method.

I need random integers in [0, 2^64). I can of course use two calls to Uint32
to do what I need, so I'm more curious than anything: why use a signed int64
as the fundamental type? Why not uint64? I skimmed the code, but I couldn't
divine the answer.

Aaron

[Russ Cox]

The generator we're using only generates 63 bits worth of output.
You're right that we probably should have corrected that before the API freeze.
Oh well.

Russ

[Aaron Jacobs]

On Wed, Oct 17, 2012 at 5:09 AM, Russ Cox <r...@golang.org> wrote:
> The generator we're using only generates 63 bits worth of output.
> You're right that we probably should have corrected that before the API freeze.
> Oh well.

Ah, well that makes sense. Is it worth filing a bug for 2.0, or whatever?

Aaron

[Rob Pike]

Please do.

[Aaron Jacobs]

On Wed, Oct 17, 2012 at 11:57 AM, Rob Pike <r...@golang.org> wrote:
> Please do.

Done. Link for posterity:

http://code.google.com/p/go/issues/detail?id=4254

[Michael Jones]

There clearly should be.

On Tue, Dec 4, 2012 at 7:40 AM, TheoDeNot <timog...@gmail.com> wrote:

Just wondering if the link posted has been taken into consideration? Just find it weird that there hasn't been a reply yet.

On Thursday, 18 October 2012 00:01:56 UTC+2, Michael Hofmann wrote:

I've written an alternative implementation of rand.Source that also has an Uint64() method. Maybe you can use it:

https://gist.github.com/3908425

Michael 

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--

Michael T. Jones | Chief Technology Advocate  | m...@google.com |  +1 650-335-5765

[Ian Lance Taylor]

On Tue, Dec 4, 2012 at 7:40 AM, TheoDeNot <timog...@gmail.com> wrote:
> Just wondering if the link posted has been taken into consideration? Just
> find it weird that there hasn't been a reply yet.

It's not clear to me what change we can make today without breaking
the Go 1 guarantee. We can't add methods to the rand.Source
interface. I suppose we could add a rand.Uint64 function that tests
whether the Source has a Uint64 method, and calls that, otherwise
calls the Int63 method twice. Does that make sense? Is it
sufficiently useful?

Ian

> On Thursday, 18 October 2012 00:01:56 UTC+2, Michael Hofmann wrote:
>>
>> On Friday, October 12, 2012 1:21:50 PM UTC+2, Aaron Jacobs wrote:
>>>

[TheoDeNot]

Yeah it makes sense to leave things the way they are now. This will work fine for now right?

package main

import (
        "fmt"
        "math/rand"
        "time"
)

func main() {
        for a := 0; a < 10; a++ {

                rand.Seed(time.Now().UTC().

UnixNano())
                t := uint64(rand.Uint32())<<32 + uint64(rand.Uint32())
                fmt.Println(t, "\n")

        }
}