• Andy Balba (6/6) Aug 09 2020 generating random numbers using
• =?UTF-8?Q?Ali_=c3=87ehreli?= (18/25) Aug 09 2020 I think feqrel() is the confusing and unnecessary part there. The
• James Blachly (5/12) Aug 10 2020 Tangential: I also find mir-random [0] a very nice library that is easy
• bachmeier (4/11) Aug 10 2020 Strange example for sure. I'd recommend checking out the examples
• bachmeier (3/15) Aug 10 2020 I created a PR with a hopefully clearer example:
• Andy Balba (3/19) Aug 10 2020 Ahhh yes, yes .. this is the way to write Dlang example code :
• Andy Balba (42/62) Aug 13 2020 ... a very neat random byte generator is at

Andy Balba <pwplus7 gmail.com> writes:

generating random numbers using 
https://dlang.org/library/std/random/uniform01.html

I find the example given in this section totally incomprehensible
.. Can any help me answer two simple questions:
How to generate a random floating number in range [0,1) ?
How to set a seed value, prior to generating random values ?

=?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:

On 8/9/20 10:51 PM, Andy Balba wrote:
 generating random numbers using 
 https://dlang.org/library/std/random/uniform01.html
 
 I find the example given in this section totally incomprehensible
 ... Can any help me answer two simple questions:
 How to generate a random floating number in range [0,1) ?
 How to set a seed value, prior to generating random values ?

I think feqrel() is the confusing and unnecessary part there. The 
following is all you need:

import std.stdio;
import std.random;

void main() {
   auto rnd = MinstdRand0(42);  // <-- Seed
   foreach (i; 0 .. 10) {
     writeln(rnd.uniform01());
   }
}

feqrel, defined at

   https://dlang.org/phobos/std_math.html#.feqrel

is used to prove that the first two floating point values generated are 
equal to 0.000328707 and 0.524587. (Check out the return value of 
feqrel, which is used in assert statements there to prove that the 
numbers are "equal" to those.)

Ali

James Blachly <james.blachly gmail.com> writes:

On 8/10/20 1:51 AM, Andy Balba wrote:
 generating random numbers using 
 https://dlang.org/library/std/random/uniform01.html
 
 I find the example given in this section totally incomprehensible
 .. Can any help me answer two simple questions:
 How to generate a random floating number in range [0,1) ?
 How to set a seed value, prior to generating random values ?

Tangential: I also find mir-random [0] a very nice library that is easy 
to use and has no deps on D runtime, so can be used in Das Better C mode.

I think it is also a better random engine than phobos

[0] https://code.dlang.org/packages/mir-random

bachmeier <no spam.net> writes:

On Monday, 10 August 2020 at 05:51:07 UTC, Andy Balba wrote:
 generating random numbers using 
 https://dlang.org/library/std/random/uniform01.html

 I find the example given in this section totally 
 incomprehensible
 .. Can any help me answer two simple questions:
 How to generate a random floating number in range [0,1) ?
 How to set a seed value, prior to generating random values ?

Strange example for sure. I'd recommend checking out the examples 
on the landing page for std.random: 
https://dlang.org/library/std/random.html

bachmeier <no spam.net> writes:

On Monday, 10 August 2020 at 14:20:23 UTC, bachmeier wrote:
 On Monday, 10 August 2020 at 05:51:07 UTC, Andy Balba wrote:
 generating random numbers using 
 https://dlang.org/library/std/random/uniform01.html

 I find the example given in this section totally 
 incomprehensible
 .. Can any help me answer two simple questions:
 How to generate a random floating number in range [0,1) ?
 How to set a seed value, prior to generating random values ?

 Strange example for sure. I'd recommend checking out the 
 examples on the landing page for std.random: 
 https://dlang.org/library/std/random.html

I created a PR with a hopefully clearer example:
https://github.com/dlang/phobos/pull/7588

Andy Balba <pwplus7 gmail.com> writes:

On Monday, 10 August 2020 at 15:13:51 UTC, bachmeier wrote:
 On Monday, 10 August 2020 at 14:20:23 UTC, bachmeier wrote:
 On Monday, 10 August 2020 at 05:51:07 UTC, Andy Balba wrote:
 generating random numbers using 
 https://dlang.org/library/std/random/uniform01.html

 I find the example given in this section totally 
 incomprehensible
 .. Can any help me answer two simple questions:
 How to generate a random floating number in range [0,1) ?
 How to set a seed value, prior to generating random values ?

 Strange example for sure. I'd recommend checking out the 
 examples on the landing page for std.random: 
 https://dlang.org/library/std/random.html

 I created a PR with a hopefully clearer example:
 https://github.com/dlang/phobos/pull/7588

Ahhh yes, yes .. this is the way to write Dlang example code :
https://dlang.org/library/std/random.html

Andy Balba <pwplus7 gmail.com> writes:

On Monday, 10 August 2020 at 15:43:04 UTC, Andy Balba wrote:
 On Monday, 10 August 2020 at 15:13:51 UTC, bachmeier wrote:
 On Monday, 10 August 2020 at 14:20:23 UTC, bachmeier wrote:
 On Monday, 10 August 2020 at 05:51:07 UTC, Andy Balba wrote:
 generating random numbers using 
 https://dlang.org/library/std/random/uniform01.html

 I find the example given in this section totally 
 incomprehensible
 .. Can any help me answer two simple questions:
 How to generate a random floating number in range [0,1) ?
 How to set a seed value, prior to generating random values ?

 Strange example for sure. I'd recommend checking out the 
 examples on the landing page for std.random: 
 https://dlang.org/library/std/random.html

 I created a PR with a hopefully clearer example:
 https://github.com/dlang/phobos/pull/7588

 Ahhh yes, yes .. this is the way to write Dlang example code :
 https://dlang.org/library/std/random.html


... a very neat random byte generator is at
  https://github.com/LightBender/SecureD/tree/master/source/secured

here's the essential code :

import std.digest;
import std.stdio;
import std.exception;

 trusted ubyte[] random (uint bytes)
{
   if (bytes == 0)
      { printf("number of bytes must be > zero"); return null; }

   ubyte[] buffer = new ubyte[bytes];

   try
   { File urandom = File("/dev/urandom", "rb");
     urandom.setvbuf (null, _IONBF);
     scope(exit) urandom.close();

     try
       { buffer= urandom.rawRead(buffer); }

     catch(ErrnoException ex)
       { printf("Cant get next random bytes"); return null;}
     catch(Exception ex)
       { printf("Cant get next random bytes"); return null; }
   }

   catch(ErrnoException ex)
     { printf("Cant initialize system RNG"); return null; }
   catch(Exception ex)
     { printf ("Cant initialize system RNG"); return null; }

return buffer;
}

void main()
{
   ubyte[] rnd1 = random(32);
   writeln("32Bytes: ", toHexString!(LetterCase.lower)(rnd1));

   ubyte[] rnd2 = random(128);
   writeln("128Bytes: ", toHexString!(LetterCase.lower)(rnd2));

   ubyte[] rnd3 = random(512);
   writeln("512Bytes:"); 
writeln(toHexString!(LetterCase.lower)(rnd3));

   ubyte[] rnd4 = random(2048);
   writeln("2048 Bytes:"); 
writeln(toHexString!(LetterCase.lower)(rnd4));

}