[Issue 4851] Three suggestions for std.random

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=4851

RazvanN  changed:

   What|Removed |Added

 Status|ASSIGNED|RESOLVED
 CC||razvan.nitu1...@gmail.com
 Resolution|--- |FIXED

--

[Issue 4851] Three suggestions for std.random

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=4851

--- Comment #13 from github-bugzi...@puremagic.com ---
Commits pushed to newCTFE at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/783d15bfa0e55d753999e7cc38236763c6b95092
enhancement issue 4851: add choice function to std.random

https://github.com/dlang/phobos/commit/adb71a6c6b8e51680ce2337eb93c28fa7ea9a3fd
enhancement issue 4851: use assert in choice function

https://github.com/dlang/phobos/commit/6bc3a4f343ab653e85d11966a4b559da59c8
Merge pull request #4897 from edi33416/implement_choice

--

[Issue 4851] Three suggestions for std.random

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=4851

--- Comment #12 from github-bugzi...@puremagic.com ---
Commits pushed to stable at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/783d15bfa0e55d753999e7cc38236763c6b95092
enhancement issue 4851: add choice function to std.random

https://github.com/dlang/phobos/commit/adb71a6c6b8e51680ce2337eb93c28fa7ea9a3fd
enhancement issue 4851: use assert in choice function

https://github.com/dlang/phobos/commit/6bc3a4f343ab653e85d11966a4b559da59c8
Merge pull request #4897 from edi33416/implement_choice

--

[Issue 4851] Three suggestions for std.random

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=4851

--- Comment #11 from github-bugzi...@puremagic.com ---
Commits pushed to scope at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/783d15bfa0e55d753999e7cc38236763c6b95092
enhancement issue 4851: add choice function to std.random

https://github.com/dlang/phobos/commit/adb71a6c6b8e51680ce2337eb93c28fa7ea9a3fd
enhancement issue 4851: use assert in choice function

https://github.com/dlang/phobos/commit/6bc3a4f343ab653e85d11966a4b559da59c8
Merge pull request #4897 from edi33416/implement_choice

--

[Issue 4851] Three suggestions for std.random

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=4851

--- Comment #10 from github-bugzi...@puremagic.com ---
Commits pushed to master at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/783d15bfa0e55d753999e7cc38236763c6b95092
enhancement issue 4851: add choice function to std.random

https://github.com/dlang/phobos/commit/adb71a6c6b8e51680ce2337eb93c28fa7ea9a3fd
enhancement issue 4851: use assert in choice function

https://github.com/dlang/phobos/commit/6bc3a4f343ab653e85d11966a4b559da59c8
Merge pull request #4897 from edi33416/implement_choice

enhancement issue 4851: add choice function to std.random

--

[Issue 4851] Three suggestions for std.random

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=4851

Eduard Staniloiu  changed:

   What|Removed |Added

   Keywords||pull

--- Comment #9 from Eduard Staniloiu  ---
I have created a PR that adds the choice function to std.random. The link is
below:

https://github.com/dlang/phobos/pull/4897

--

[Issue 4851] Three suggestions for std.random

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=4851

Andrei Alexandrescu  changed:

   What|Removed |Added

   Assignee|nob...@puremagic.com|edi33...@gmail.com

--

[Issue 4851] Three suggestions for std.random

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=4851

Andrei Alexandrescu  changed:

   What|Removed |Added

   Keywords||bootcamp

--- Comment #8 from Andrei Alexandrescu  ---
Adding some of my own:

* uniform!int should give a uniform, full-range int. Same of course for all
integral types.

* uniform!bool should give a random bit (economically, i.e. generate a new
64-bit number every 64 calls)

* uniform!double should give a double in the range [0.0, 1.0). Or is [0.0, 1.0]
more appropriate?

* uniform!(int[])(30) should return an array of 30 integers

* uniform!string(30) should return a uniform string of 30... bytes or code
points?

--

[Issue 4851] Three suggestions for std.random

[d-bugmail]

https://d.puremagic.com/issues/show_bug.cgi?id=4851



--- Comment #7 from bearophile_h...@eml.cc 2014-03-29 16:13:21 PDT ---
If choice returns a reference you can do:


void knuthShuffle(T)(T[] r) {
foreach_reverse (immutable i, ref ri; r[1 .. $ - 1])
r[0 .. i + 1].choice.swap(ri);
}

-- 
Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email
--- You are receiving this mail because: ---

[Issue 4851] Three suggestions for std.random

[d-bugmail]

http://d.puremagic.com/issues/show_bug.cgi?id=4851


jens.k.muel...@gmx.de changed:

   What|Removed |Added

 CC||jens.k.muel...@gmx.de


--- Comment #3 from jens.k.muel...@gmx.de 2013-02-23 05:12:55 PST ---
How much of this request is still valid?
From the documentation I find that
1. randomShuffle has default random generator
2. same for randomSample via overloads
3. choice can be expressed via
   auto choice = () = randomSample(r, 1, r.length).front;

Missing piece is randomCover with a default RandomGen.

Is this correct?

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
--- You are receiving this mail because: ---

[Issue 4851] Three suggestions for std.random

[d-bugmail]

http://d.puremagic.com/issues/show_bug.cgi?id=4851


bearophile_h...@eml.cc changed:

   What|Removed |Added

 AssignedTo|and...@erdani.com   |nob...@puremagic.com


--- Comment #4 from bearophile_h...@eml.cc 2013-02-23 05:24:37 PST ---
(In reply to comment #3)

 3. choice can be expressed via
auto choice = () = randomSample(r, 1, r.length).front;

That looks bad and it's error prone. It's not a replacement for choice() (and
you have missed the input argument r).


 Missing piece is randomCover with a default RandomGen.

Right.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
--- You are receiving this mail because: ---

[Issue 4851] Three suggestions for std.random

[d-bugmail]

http://d.puremagic.com/issues/show_bug.cgi?id=4851



--- Comment #5 from jens.k.muel...@gmx.de 2013-02-23 05:49:23 PST ---
(In reply to comment #4)
 (In reply to comment #3)
 
  3. choice can be expressed via
 auto choice = () = randomSample(r, 1, r.length).front;
 
 That looks bad and it's error prone. It's not a replacement for choice() (and
 you have missed the input argument r).

Right.
Just for clarification. Adding

auto choice(R)(R r) { return randomSample(r, 1, r.length).front; };

would be fine?

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
--- You are receiving this mail because: ---

[Issue 4851] Three suggestions for std.random

[d-bugmail]

http://d.puremagic.com/issues/show_bug.cgi?id=4851



--- Comment #6 from bearophile_h...@eml.cc 2013-02-23 09:45:45 PST ---
(In reply to comment #5)

 Just for clarification. Adding
 
 auto choice(R)(R r) { return randomSample(r, 1, r.length).front; };
 
 would be fine?

When the input is an array (Random access range) I'd like it to use a
items[uniform(0, $)]. So it's faster for the most common use case.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
--- You are receiving this mail because: ---

[Issue 4851] Three suggestions for std.random

[d-bugmail]

http://d.puremagic.com/issues/show_bug.cgi?id=4851



--- Comment #2 from bearophile_h...@eml.cc 2011-04-16 12:54:38 PDT ---
That fourth idea is also useful to avoid a little trap. This code looks
correct, here randomCover() is used to act like the Python random.choice(), but
here it keeps taking the same value:

import std.stdio, std.random;
void main() {
// can't be const
/*const*/ int[] data = [1, 2, 3, 4];
foreach (i; 0 .. 20) {
int r = randomCover(data, rndGen).front;
write(r,  );
}
}

Output:
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1


The same bug can't happen with code like this, because the random generator is
not created inside the foreach scope:

import std.stdio, std.random;
void main() {
// can't be const
/*const*/ int[] data = [1, 2, 3, 4];
foreach (i; 0 .. 20) {
int r = randomCover(data).front;
// int r = choice(data); // better
write(r,  );
}
}

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
--- You are receiving this mail because: ---

[Issue 4851] Three suggestions for std.random

[d-bugmail]

http://d.puremagic.com/issues/show_bug.cgi?id=4851


Andrei Alexandrescu and...@metalanguage.com changed:

   What|Removed |Added

 Status|NEW |ASSIGNED
 CC||and...@metalanguage.com
 AssignedTo|nob...@puremagic.com|and...@metalanguage.com


-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
--- You are receiving this mail because: ---

[Issue 4851] Three suggestions for std.random

[d-bugmail]

http://d.puremagic.com/issues/show_bug.cgi?id=4851



--- Comment #1 from bearophile_h...@eml.cc 2010-09-12 18:56:32 PDT ---
A fourth possible idea:
RandomCover!(R, RandomGen) randomCover(R, RandomGen=Random)(R r, RandomGen
gen=rndGen);

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
--- You are receiving this mail because: ---