Random generator fail

[Anonymous Monk]

I am trying generate 100 random numbers using forach

between 1 thru 99

But always get between 0 and 1. Any ideas?

perl -wle "use 5.10.0;  say  rand foreach(1..100) ;"

Thanks.

[MidLifeXis]

See the documentation for rand. It explains pretty well why this is happening.

[blue_cowdawg]

But always get between 0 and 1. Any ideas?

Works as designed.

$ perl -e 'use 5.10.0; say int(6*rand())+1 foreach(1..10);'
6
5
4
6
2
2
4
6
3
5

Is that what you were after? Or at least something like it?

As MidLifeXis pointed out:

       rand EXPR
       rand    Returns a random fractional number greater than or equa
+l to 0
               and less than the value of EXPR.  (EXPR should be posit
+ive.)
               If EXPR is omitted, the value 1 is used.  Currently EXP
+R with
               the value 0 is also special-cased as 1 (this was undocu
+mented
               before Perl 5.8.0 and is subject to change in future ve
+rsions
               of Perl).  Automatically calls "srand" unless "srand" h
+as
               already been called.  See also "srand".

               Apply "int()" to the value returned by "rand()" if you 
+want
               random integers instead of random fractional numbers.  
+For
               example,

                   int(rand(10))

               returns a random integer between 0 and 9, inclusive.

               (Note: If your rand function consistently returns numbe
+rs that
               are too large or too small, then your version of Perl w
+as
               probably compiled with the wrong number of RANDBITS.)

               "rand()" is not cryptographically secure.  You should n
+ot rely
               on it in security-sensitive situations.  As of this wri
+ting, a
               number of third-party CPAN modules offer random number
               generators intended by their authors to be cryptographi
+cally
               secure, including: Math::Random::Secure,
               Math::Random::MT::Perl, and Math::TrulyRandom.

[BillKSmith]

Do you want real numbers in the range (1 <= number < 99) on a windows system?

perl -e"print 1 + rand 98, qq(\n) for 1..100"

[Anonymous Monk]

Ok I have better understanding now, Bill your solutions works great!

@MidLifeXis What is rational for rand to ignore $_. Appearently you pointing out that, solves my problem by using

perl -wle "use 5.10.0;  foreach (1..100) { say rand($_);};"

1.94992065429688
56.7288208007813
52.1597290039063
18.6995849609375
6.6961669921875
68.6776733398438
65.6177978515625
62.72314453125
52.1324157714844
...

But I think using additional line  { say rand($_); is completely un-neccessary. Thank you.

[MidLifeXis]

Let's step through this:

foreach (1..100) {
    say rand($_);
}

When $_ is equal to ...
• ... 1, rand($_) cannot be larger than 1.
• ... 2, rand($_) cannot be larger than 2.
• ... 3, rand($_) cannot be larger than 3.
• ... 4, rand($_) cannot be larger than 4.
• ... 5, rand($_) cannot be larger than 5.
• ... 6, rand($_) cannot be larger than 6.

Look at one of my earlier posts on this thread. The documentation for rand states that 0 <= rand($x) < $x if $x > 0. To accomplish what you are trying to do would require that you do this:

say 1 + rand(99 - 1) for (1..100)

In my previous node, MAX = 99 and MIN = 1. The 1..100 is the number of iterations you wish to use. If you use rand($_), your results will be biased toward the lower end of the counter range.

[BillKSmith]

My rand 98 generates random numbers in the range (0<= number < 98). Adding one to every random number changes the range to (1<=number<99). Using rand $_ would generate a very different sequence of numbers. In fact, the sample output that you show cannot be the first few numbers as your dots suggest. It is possible that they are the last few numbers.

[Anonymous Monk]

forgot to add this:

perl -wle "use 5.10.0;   say int foreach (1..100) ;"

Works as rand() should have.

[kcott]

Here's my $0.02 worth:

$ perl -E 'say 1 + int rand 99 for 1..3'
28
94
43

Obviously, change the 3 to 100.

Update: You appear to want decimals although you asked for a range using integers. Perhaps you could clarify.

This gives: 1.0 < random_number < 99.0

$ perl -E 'say 1 + rand 98 for 1..3'
38.6240726329874
72.0054041794683
94.0423383452302