Here's what I got so far. The code's not great, can it be improved?

Can you think of a set of inputs that will exercise it better? (Note: I haven't got around to log() scales yet.) 

#! perl -slw
use strict;

sub log10{ log( $_[0] ) / log( 10 ) }

sub ticks {
    my( $start, $end, $n ) = @_;
    $n ||= 10;
    my $range = $end - $start;
    $range += $range / $n;
    my $interval = $range / $n;
    $interval  = 10**int( log10( $interval ) );
    $interval *= 10 while ( $range / $interval ) > ( $n * 2 );
    $interval /=  2 while ( $range / $interval ) < ( $n / 2 );
    $start = int( $start / $interval ) * $interval;

    my @ticks;
    while( $start < ( $end + $interval ) ) {
        push @ticks, $start;
        $start += $interval;
    }
    return @ticks;
}


for my $range (
    [0,9], [0.123,8.673], [0.022, 0.086],
    [1_123_345_456, 1_124_246_357.5], [1_123_345_456, 1_123_346_357.5]
+,
    [ 0.00011, 0.00041],
) {
    for my $n ( 0, 4, 5, 8 , 10, 15, 16, 20, 21 ) {
        my @ticks = ticks( @$range, $n );

        printf "from:%12.12g to %12.12g by:%2u -> [%2u][ %s ]\n",
            @$range, $n, scalar( @ticks ), join ' ', map{
                my $s = sprintf( "%.8g", $_ ); $s =~ s[e([+-])0*([1-9]
++)]['e' . ($1 eq '-' ? '-' : '') . $2]e;
                $s;
            } @ticks;

    }
}

[download]

Output:

C:\test>calcTicks.pl
from:           0 to            9 by: 0 -> [10][ 0 1 2 3 4 5 6 7 8 9 ]
from:           0 to            9 by: 4 -> [ 3][ 0 5 10 ]
from:           0 to            9 by: 5 -> [ 5][ 0 2.5 5 7.5 10 ]
from:           0 to            9 by: 8 -> [10][ 0 1 2 3 4 5 6 7 8 9 ]
from:           0 to            9 by:10 -> [10][ 0 1 2 3 4 5 6 7 8 9 ]
from:           0 to            9 by:15 -> [10][ 0 1 2 3 4 5 6 7 8 9 ]
from:           0 to            9 by:16 -> [10][ 0 1 2 3 4 5 6 7 8 9 ]
from:           0 to            9 by:20 -> [19][ 0 0.5 1 1.5 2 2.5 3 3
+.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 ]
from:           0 to            9 by:21 -> [19][ 0 0.5 1 1.5 2 2.5 3 3
+.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 ]
from:       0.123 to        8.673 by: 0 -> [10][ 0 1 2 3 4 5 6 7 8 9 ]
from:       0.123 to        8.673 by: 4 -> [ 3][ 0 5 10 ]
from:       0.123 to        8.673 by: 5 -> [ 5][ 0 2.5 5 7.5 10 ]
from:       0.123 to        8.673 by: 8 -> [10][ 0 1 2 3 4 5 6 7 8 9 ]
from:       0.123 to        8.673 by:10 -> [10][ 0 1 2 3 4 5 6 7 8 9 ]
from:       0.123 to        8.673 by:15 -> [10][ 0 1 2 3 4 5 6 7 8 9 ]
from:       0.123 to        8.673 by:16 -> [10][ 0 1 2 3 4 5 6 7 8 9 ]
from:       0.123 to        8.673 by:20 -> [19][ 0 0.5 1 1.5 2 2.5 3 3
+.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 ]
from:       0.123 to        8.673 by:21 -> [19][ 0 0.5 1 1.5 2 2.5 3 3
+.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 ]
from:       0.022 to        0.086 by: 0 -> [ 8][ 0.02 0.03 0.04 0.05 0
+.06 0.07 0.08 0.09 ]
from:       0.022 to        0.086 by: 4 -> [ 5][ 0 0.025 0.05 0.075 0.
+1 ]
from:       0.022 to        0.086 by: 5 -> [ 5][ 0 0.025 0.05 0.075 0.
+1 ]
from:       0.022 to        0.086 by: 8 -> [ 8][ 0.02 0.03 0.04 0.05 0
+.06 0.07 0.08 0.09 ]
from:       0.022 to        0.086 by:10 -> [ 8][ 0.02 0.03 0.04 0.05 0
+.06 0.07 0.08 0.09 ]
from:       0.022 to        0.086 by:15 -> [15][ 0.02 0.025 0.03 0.035
+ 0.04 0.045 0.05 0.055 0.06 0.065 0.07 0.075 0.08 0.085 0.09 ]
from:       0.022 to        0.086 by:16 -> [15][ 0.02 0.025 0.03 0.035
+ 0.04 0.045 0.05 0.055 0.06 0.065 0.07 0.075 0.08 0.085 0.09 ]
from:       0.022 to        0.086 by:20 -> [15][ 0.02 0.025 0.03 0.035
+ 0.04 0.045 0.05 0.055 0.06 0.065 0.07 0.075 0.08 0.085 0.09 ]
from:       0.022 to        0.086 by:21 -> [15][ 0.02 0.025 0.03 0.035
+ 0.04 0.045 0.05 0.055 0.06 0.065 0.07 0.075 0.08 0.085 0.09 ]
from:  1123345456 to 1124246357.5 by: 0 -> [11][ 1.1233e9 1.1234e9 1.1
+235e9 1.1236e9 1.1237e9 1.1238e9 1.1239e9 1.124e9 1.1241e9 1.1242e9 1
+.1243e9 ]
from:  1123345456 to 1124246357.5 by: 4 -> [ 4][ 1.123e9 1.1235e9 1.12
+4e9 1.1245e9 ]
from:  1123345456 to 1124246357.5 by: 5 -> [ 5][ 1.12325e9 1.1235e9 1.
+12375e9 1.124e9 1.12425e9 ]
from:  1123345456 to 1124246357.5 by: 8 -> [11][ 1.1233e9 1.1234e9 1.1
+235e9 1.1236e9 1.1237e9 1.1238e9 1.1239e9 1.124e9 1.1241e9 1.1242e9 1
+.1243e9 ]
from:  1123345456 to 1124246357.5 by:10 -> [11][ 1.1233e9 1.1234e9 1.1
+235e9 1.1236e9 1.1237e9 1.1238e9 1.1239e9 1.124e9 1.1241e9 1.1242e9 1
+.1243e9 ]
from:  1123345456 to 1124246357.5 by:15 -> [11][ 1.1233e9 1.1234e9 1.1
+235e9 1.1236e9 1.1237e9 1.1238e9 1.1239e9 1.124e9 1.1241e9 1.1242e9 1
+.1243e9 ]
from:  1123345456 to 1124246357.5 by:16 -> [11][ 1.1233e9 1.1234e9 1.1
+235e9 1.1236e9 1.1237e9 1.1238e9 1.1239e9 1.124e9 1.1241e9 1.1242e9 1
+.1243e9 ]
from:  1123345456 to 1124246357.5 by:20 -> [20][ 1.1233e9 1.12335e9 1.
+1234e9 1.12345e9 1.1235e9 1.12355e9 1.1236e9 1.12365e9 1.1237e9 1.123
+75e9 1.1238e9 1.12385e9 1.1239e9 1.12395e9 1.124e9 1.12405e9 1.1241e9
+ 1.12415e9 1.1242e9 1.12425e9 ]
from:  1123345456 to 1124246357.5 by:21 -> [20][ 1.1233e9 1.12335e9 1.
+1234e9 1.12345e9 1.1235e9 1.12355e9 1.1236e9 1.12365e9 1.1237e9 1.123
+75e9 1.1238e9 1.12385e9 1.1239e9 1.12395e9 1.124e9 1.12405e9 1.1241e9
+ 1.12415e9 1.1242e9 1.12425e9 ]
from:  1123345456 to 1123346357.5 by: 0 -> [11][ 1.1233454e9 1.1233455
+e9 1.1233456e9 1.1233457e9 1.1233458e9 1.1233459e9 1.123346e9 1.12334
+61e9 1.1233462e9 1.1233463e9 1.1233464e9 ]
from:  1123345456 to 1123346357.5 by: 4 -> [ 4][ 1.123345e9 1.1233455e
+9 1.123346e9 1.1233465e9 ]
from:  1123345456 to 1123346357.5 by: 5 -> [ 6][ 1.1233453e9 1.1233455
+e9 1.1233458e9 1.123346e9 1.1233463e9 1.1233465e9 ]
from:  1123345456 to 1123346357.5 by: 8 -> [11][ 1.1233454e9 1.1233455
+e9 1.1233456e9 1.1233457e9 1.1233458e9 1.1233459e9 1.123346e9 1.12334
+61e9 1.1233462e9 1.1233463e9 1.1233464e9 ]
from:  1123345456 to 1123346357.5 by:10 -> [11][ 1.1233454e9 1.1233455
+e9 1.1233456e9 1.1233457e9 1.1233458e9 1.1233459e9 1.123346e9 1.12334
+61e9 1.1233462e9 1.1233463e9 1.1233464e9 ]
from:  1123345456 to 1123346357.5 by:15 -> [11][ 1.1233454e9 1.1233455
+e9 1.1233456e9 1.1233457e9 1.1233458e9 1.1233459e9 1.123346e9 1.12334
+61e9 1.1233462e9 1.1233463e9 1.1233464e9 ]
from:  1123345456 to 1123346357.5 by:16 -> [11][ 1.1233454e9 1.1233455
+e9 1.1233456e9 1.1233457e9 1.1233458e9 1.1233459e9 1.123346e9 1.12334
+61e9 1.1233462e9 1.1233463e9 1.1233464e9 ]
from:  1123345456 to 1123346357.5 by:20 -> [20][ 1.1233455e9 1.1233455
+e9 1.1233456e9 1.1233456e9 1.1233457e9 1.1233457e9 1.1233458e9 1.1233
+458e9 1.1233459e9 1.1233459e9 1.123346e9 1.123346e9 1.1233461e9 1.123
+3461e9 1.1233462e9 1.1233462e9 1.1233463e9 1.1233463e9 1.1233464e9 1.
+1233464e9 ]
from:  1123345456 to 1123346357.5 by:21 -> [20][ 1.1233455e9 1.1233455
+e9 1.1233456e9 1.1233456e9 1.1233457e9 1.1233457e9 1.1233458e9 1.1233
+458e9 1.1233459e9 1.1233459e9 1.123346e9 1.123346e9 1.1233461e9 1.123
+3461e9 1.1233462e9 1.1233462e9 1.1233463e9 1.1233463e9 1.1233464e9 1.
+1233464e9 ]
from:     0.00011 to      0.00041 by: 0 -> [ 8][ 0.0001 0.00015 0.0002
+ 0.00025 0.0003 0.00035 0.0004 0.00045 ]
from:     0.00011 to      0.00041 by: 4 -> [ 5][ 0.0001 0.0002 0.0003 
+0.0004 0.0005 ]
from:     0.00011 to      0.00041 by: 5 -> [ 5][ 0.0001 0.0002 0.0003 
+0.0004 0.0005 ]
from:     0.00011 to      0.00041 by: 8 -> [ 8][ 0.0001 0.00015 0.0002
+ 0.00025 0.0003 0.00035 0.0004 0.00045 ]
from:     0.00011 to      0.00041 by:10 -> [ 8][ 0.0001 0.00015 0.0002
+ 0.00025 0.0003 0.00035 0.0004 0.00045 ]
from:     0.00011 to      0.00041 by:15 -> [14][ 0.0001 0.000125 0.000
+15 0.000175 0.0002 0.000225 0.00025 0.000275 0.0003 0.000325 0.00035 
+0.000375 0.0004 0.000425 ]
from:     0.00011 to      0.00041 by:16 -> [14][ 0.0001 0.000125 0.000
+15 0.000175 0.0002 0.000225 0.00025 0.000275 0.0003 0.000325 0.00035 
+0.000375 0.0004 0.000425 ]
from:     0.00011 to      0.00041 by:20 -> [14][ 0.0001 0.000125 0.000
+15 0.000175 0.0002 0.000225 0.00025 0.000275 0.0003 0.000325 0.00035 
+0.000375 0.0004 0.000425 ]
from:     0.00011 to      0.00041 by:21 -> [14][ 0.0001 0.000125 0.000
+15 0.000175 0.0002 0.000225 0.00025 0.000275 0.0003 0.000325 0.00035 
+0.000375 0.0004 0.000425 ]

[download]
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority". I'm with torvalds on this
In the absence of evidence, opinion is indistinguishable from prejudice. Agile (and TDD) debunked

In reply to Re: Simple calculation. (A solution; can it be improved/broken?) by BrowserUk
in thread Simple calculation. by BrowserUk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.