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In this node, tall_man asked how to generate the Hamming Sequence lazily in Perl5. I didn't understand the Haskell code and misunderstood the english explanation.

"how do you generate the series of numbers composed of a given list of prime factors, where each can be used an unlimited number of times?"

I interpreted that to mean all multiples of all prime factors provided minus duplicates were valid. My mistake was exacerbated by the fact the sample series provided fit my interpretation. I took my licks after posting an incorrect solution.

I was happy to take the downvotes and be wrong since the mistake was just as interesting to me. My challenge then is to produce R as shown below for any set of given factors lazily:

```Given:  Factors 2, 3, 5
2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, ...
3, 6, 9, 12, 15, 18, 21, 24, 27, 30, ...
5, 10, 15, 20, 25, 30, ...

R = 2, 3, 4, 5, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 2
+6, 27, 28, 30, ...
You can see my cleaned up solution below:
```#!/usr/bin/perl
use strict;
use warnings;

use constant TAIL => -1;

my \$end = shift || 10;
my @num = @ARGV ? @ARGV : (2, 3, 5);
my \$next = merge_multiple( \@num );

print \$next->(), "\n" for 1 .. \$end;

sub merge_multiple {
my \$list = shift;
return () if ! \$list || ref \$list ne 'ARRAY';

my \$n = 1;
my \$h = \$list->[TAIL];
my (@pool, @stream);

return sub {
return shift @pool if @pool;

for ( 0 .. \$#\$list ) {
my \$mult = \$list->[ \$_ ];
my \$beg = \$h * (\$n - 1) / \$mult + 1;
my \$end = \$h * \$n / \$mult;
\$stream[ \$_ ] = [ map { \$mult * \$_ } \$beg .. \$end ];
}
++\$n;

@pool = merge( \@stream );
return shift @pool;
}
}

sub merge {
my \$stream = shift;
my \$end = \$#\$stream;

my @merged;
while ( 1 ) {
my \$low;
for ( 0 .. \$end ) {
my \$val = \$stream->[ \$_ ][HEAD];
next if ! defined \$val;
\$low = \$_ if ! defined \$low || \$val < \$stream->[ \$low ][HE
}
last if ! defined \$low;
my \$num = shift @{ \$stream->[ \$low ] };
next if defined \$merged[ TAIL ] && \$merged[ TAIL ] == \$num;
push @merged, \$num;
}
return @merged;
}

Cheers - L~R

In reply to Challenge: Another Infinite Lazy List by Limbic~Region

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