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Re: Hamming Sequences and Lazy Lists

by BrowserUk (Pope)
on Mar 17, 2005 at 08:34 UTC ( #440299=note: print w/ replies, xml ) Need Help??

in reply to Hamming Sequences and Lazy Lists

This horribly inefficient brute-force conversion seems like it's getting close, but needs work.

#! perl -slw use strict; sub merge { return unless @_ == 2; return @{ $_[1] } unless @{ $_[0] }; return @{ $_[0] } unless @{ $_[1] }; my( $x, $y ) = ( $_[0][0], $_[1][0] ); return shift @{ $_[0] }, merge( @_ ) if $x < $y; return shift @{ $_[1] }, merge( @_ ) if $x > $y; shift @{ $_[0] }; return shift @{ $_[1] }, merge( @_ ); } my @out; sub genHam { return unless @_; my( $x, @xs ) = @_; return @out = merge [ 1, map{ $_*$x } @out ], [ genHam( @xs ) ]; } print join'|',genHam 2, 3, 5 for 1..5; __END__ [ 8:26:05.53] P:\test>440284 1 1|2|3|5 1|2|3|4|5|6|9|10|15|25 1|2|3|4|5|6|8|9|10|12|15|18|20|25|27|30|45|50|75|125 1|2|3|4|5|6|8|9|10|12|15|16|18|20|24|25|27|30|36|40|45|50|54|60|75|81| +90|100|125|135|150|225|250|375|625

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Re^2: Hamming Sequences and Lazy Lists
by Limbic~Region (Chancellor) on Mar 17, 2005 at 16:52 UTC
    I don't follow the results? It is my understanding that the results should be the multiples of all 3 factors merged with duplicates removed. Since the list is infinite, the list should be lazy only calculating what is needed. See Re: Hamming Sequences and Lazy Lists for my understanding an implementation of the problem.

    Cheers - L~R

    Update: I still don't understand your output, but my understanding of the Hamming Sequence is wrong. I was so focused on lazy evaluation that I misunderstood "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?" To me, that meant any positive multiple of any factor was valid.

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