PERL Beginners - problem with the do-until loop

Author

problem with the do-until loop

Mei

2005-06-06, 3:56 pm

Hi,

I want to generate 6 random numbers from 1 to 10.

The 6 numbers must not the same.

These numbers must match to the number of an array.

I like to know how many iterations to get the match.

I am having troubles with the do-until loop. Could someone point out the
problem for me?

#!/usr/bin/perl -w

# generate 6 random numbers (1~10) that match exactly to the @ticket

# count the number of loops

use strict;

srand(time||$$);

my @ticket = sort (2, 3, 5, 7, 8, 10);

my @all_number = ();

my @new_number = ();

my $count = 0;

# generate 10 numbers

for (my $i = 0; $i < 10; $i++) {

my $number = $i + 1;

push (@all_number, $number)

}

do {

#reset @new_number to the empty array each time through the loop.

@new_number = ();

#get 6 random numbers

for (my $i = 0; $i < 6; $i++) {

my $position = randomposition (@all_number);

# Pick a random number from @all_number

my $number = splice (@all_number, $position, 1);

push (@new_number, $number);

}

@new_number = sort (@new_number);

print "@new_number\n";

$count++;

} until (($new_number[0] eq "$ticket[0]") && ($new_number[1] eq
"$ticket[1]")

&& ($new_number[2] eq "$ticket[2]") && ($new_number[3] eq
"$ticket[3]")

&& ($new_number[4] eq "$ticket[4]") && ($new_number[5] eq
"$ticket[5]"));

print $count, "\n";

########################################
##################

sub randomposition {

my(@all_number) = @_;

# This expression returns a random number

return int(rand(scalar(@all_number)));

}

mi.gg@alma.ch

2005-06-08, 3:57 am

It may all become much simpler once the syntax is cleaned up and
simplified.

For example, you can reduce

> my @all_number = ();
....
> # generate 10 numbers
>
> for (my $i = 0; $i < 10; $i++) {
>
> my $number = $i + 1;
>
> push (@all_number, $number)
>
> }

to

my @all_number = (1..10);

and reduce

> #get 6 random numbers
>
> for (my $i = 0; $i < 6; $i++) {
>
> my $position = randomposition (@all_number);
>
> # Pick a random number from @all_number
>
> my $number = splice (@all_number, $position, 1);
>
> push (@new_number, $number);
>
> }

to

for (1..6) {
push @new_number, randomposition;
}

and

> sub randomposition {
>
> my(@all_number) = @_;
>
> # This expression returns a random number
>
> return int(rand(scalar(@all_number)));
>
> }

to

sub randomposition {
# return random number between 1 and 10;
return int(rand 10)+1;
}

But I still don't quite understand what you are trying to accomplish.

Do you want to count how many tries it takes to get a copy of an array
by generating random numbers? What for? The count you would get will be
random anyway. There are statistical functions for this sort of thing.
Or maybe I completely misunderstood your purpose.

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