Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

My program accepts 3 percentile inputs ($pre, $amble, $post ) which should sum to 100, if they don't I wish to correct them such that they do.

If the sum is greater than 100 I wish to favour amble, then pre, then post.

If the sum is less than 100, post takes up the slack;

The following achieves my aim, but it doesn't seem very elegant (perlish), and I am sure that it can be improved upon. 

$pre = (shift) % 100;
$amble = (shift) % 100;
$post = (shift) % 100;    
if ($pre + $amble + $post != 100 ) {
    $pre = 100 - $amble 
           if ( $amble + $pre > 100 );
    $post =  100 - ($amble + $pre) 
           if ( $pre + $amble + $post != 100 );
}
print "$pre + $amble + $post = ", <br>
$pre + $amble + $post , "\n";

[download]
When is p the complement of ch?
When in the company of Erlish!

Replies are listed 'Best First'.
Re: Not very Perlish? (note the capital P ;)
by frankus (Priest) on Jun 10, 2002 at 10:13 UTC
    As a wearer of size eleven paratrooper boots, I think elegance is over rated. As cranky Perl coder, my philostophy is this: 
    If it works, it's Perl.

    If you still want a more Perlish way, you're throwing down the gauntlet for Perl Golf. Bad anonymous monk!. 

    my @items = map {$_ % 100 } @_;
my $sum = 100;
$sum -= $_ for @items[0..2];
$items[ $sum<0?0:2 ] += $sum unless $sum == 0;

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    --

    Brother Frankus.

    ¤

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Re: Not very perlish?
by Abigail-II (Bishop) on Jun 10, 2002 at 11:37 UTC
    Here's a Perl program that takes N numbers and scales them such that their sum becomes 100, but their ratios remain the same.

    Abigail 

    #!/usr/bin/perl

use strict;
use warnings 'all';

my $sum  = 0;
   $sum += $_ for @ARGV;

map {$_ *= 100 / $sum} @ARGV;

print "@ARGV\n";

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(tye)Re: Not very perlish?
by tye (Sage) on Jun 10, 2002 at 16:48 UTC

    I think you have an excellent start. You can simplify it a fair bit, however: 

        my $pre = (shift) % 100;
    my $amble = (shift) % 100;
    my $post = (shift) % 100;
    $pre = 100 - $amble   if( $amble + $pre > 100 );
    $post = 100 - ($amble + $pre);
    print "$pre + $amble + $post = ",
        $pre + $amble + $post , "\n";

    [download]
    That should produce the same results modulo round-off errors.

            - tye (but my friends call me "Tye")
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Re: Not very perlish?
by particle (Vicar) on Jun 10, 2002 at 11:56 UTC
    If the sum is greater than 100 I wish to favour amble, then pre, then post.

    If the sum is less than 100, post takes up the slack;

    i think this will do it. if amble is greater than 100, it's an error. otherwise, an array will be returned with the values as you specify above. i used the values directly from the @_ array, to make sure they were constant. if you have trouble, i can de-obfuscate it.

    sub verify_percentile
{
  my $tot = 100;
  $_[1] > $tot && die('out of range');
  return $_[0] + $_[1] > $tot
    ? ( $tot - $_[1], $_[1], 0)
    : (@_[0,1], $tot - $_[0] - $_[1]);
}

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    ~Particle *accelerates*

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Re: Not very perlish?
by talexb (Chancellor) on Jun 10, 2002 at 14:30 UTC
    Here's another approach. 
    {
  #  Arguments to this function are in the order Pre, 
  #  Amble, and Post. Not sure why we're doing a modulo
  #  100 operation here unless it's a substitution for
  #  the int() operator.

  my $Sum = 0;
  my @Values = map { $_ % 100, $Sum += $_, $_; } @_;

  if ( $Sum > 100 )
  {
    #  "If the sum is greater than 100 I wish to favour
    #  amble, then pre, then post."

    my @Index = ( 1, 0, 2 );
    my $ThisElement = 0;

    #  Reduce values in selected order by brute force.
    #  This could be done by calculation instead.

    while ( $Sum > 100 )
    {
      $Values[ $Index[ $ThisElement++ % 3 ] ]--;
      $Sum--;
    }
  }
  elsif ( $Sum < 100 )
  {
    #  "If the sum is less than 100, post takes up the
    #  slack;"

    $Values[ 2 ] -= 100 - $Sum;
  }

  #  In all cases, return the variables, modified or not.

  return ( @Values );
}

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    Code is not tested.

    --t. alex

    "Nyahhh (munch, munch) What's up, Doc?" --Bugs Bunny

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Re: Not very perlish?
by Anonymous Monk on Jun 10, 2002 at 23:54 UTC

    One post - replies to several good brethren and sisthren.

    >Re: Not very Perlish? (note the capital P ;) - Noted!

    >If it works, it's Perl. - True - but I wish to extend my knowledge

    > you're throwing down the gauntlet for Perl Golf. - Que? "Perl Golf"? 

    my @items = map {$_ % 100 } @_;
my $sum = 100;
$sum -= $_ for @items[0..2];
$items[ $sum<0?0:2 ] += $sum unless $sum == 0;

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    Neat! i *think* I understand this.

    Brother Frankus. - Thankyou.

    Here's a Perl program that takes N numbers and scales them such that their sum becomes 100, but their ratios remain the same.

    - Probably what I was unconciously seeking.

    Abigail - Thankyou. This is what I will be using!

    ~Particle *accelerates* - I need to sanitise all inputs and continue to run. - probably an easy mod IF I understood how yours worked :)

    Not sure why we're doing a modulo 100 operation here unless it's a substitution for the int() operator.

    Seemed like the easy way to
    a) force values <100
    b) deal with non-integer inputs?

    --t. alex - Thankyou.

    > I think you have an excellent start - Is this "faint praise" ? :)

    >. You can simplify it a fair bit, however: - And in a couple of (now you pointed them out!) very obvious ways.

    - tye (but my friends call me "Tye") - Thanyou! (May I call you Tye?:)

    When is P the compliment of ch?
    When they are in the company of Erlish!

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