NAME¶

Math::PlanePath::Base::Digits -- helpers for digit based paths

SYNOPSIS¶

 use Math::PlanePath::Base::Digits 'digit_split_lowtohigh';
 foreach my $digit (digit_split_lowtohigh ($n, 16)) {
 }

DESCRIPTION¶

This is a few generic helper functions for paths based on digits or powering. They're designed to work on plain Perl integers and floats and there's some special case support for "Math::BigInt".

EXPORTS¶

Nothing is exported by default but each function below can be as in the usual Exporter style,

    use Math::PlanePath::Base::Digits 'round_down_pow';

(But not "parameter_info_radix2()", for the reason described below.)

FUNCTIONS¶

Generic¶

"($power, $exponent) = round_down_pow ($n, $radix)"

Return the power of $radix equal to or less than $n. For example

   ($pow, $exp) = round_down_pow (260, 2);
   # $pow==256  # the next lower power
   # $exp==8    # the exponent in that power
   # 2**8=256 is next below 260
    

"@digits = digit_split_lowtohigh ($n, $radix)"

"@bits = bit_split_lowtohigh ($n)"

Return a list of digits from $n in base $radix, or in binary. For example,

   @digits = digit_split_lowtohigh (12345, 10);
   # @digits = (5,4,3,2,1)   # decimal digits low to high
    

If "$n==0" then the return is an empty list. The current code expects "$n >= 0".

"lowtohigh" in the name tries to make it clear which way the digits are returned. "reverse()" can be used to get high to low instead (see "reverse" in perlfunc).

"bit_split_lowtohigh()" is the same as "digit_split_lowtohigh()" called with radix=2.

"$n = digit_join_lowtohigh ($arrayref, $radix)"

"$n = digit_join_lowtohigh ($arrayref, $radix, $zero)"

Return a value made by joining digits from $arrayref in base $radix. For example,

   @digits = (5,4,3,2,1)   # decimal digits low to high
   $n = digit_split_lowtohigh (\@digits, 10);
   # $n == 12345
    

Optional $zero can be a 0 of an overloaded number type such as "Math::BigInt" to give a returned $n of that type.

Subclassing¶

"$aref = parameter_info_array()"

Return an arrayref of a "radix" parameter, default 2. This is designed to be imported into a PlanePath subclass as its "parameter_info_array()" method.

    package Math::PlanePath::MySubclass;
    use Math::PlanePath::Base::Digits 'parameter_info_array';
    

The arrayref is

    [ { name      => 'radix',
        share_key => 'radix_2',
        display   => 'Radix',
        type      => 'integer',
        minimum   => 2,
        default   => 2,
        width     => 3,
        description => 'Radix (number base).',
      }
    ]
    

"$href = Math::PlanePath::Base::Digits::parameter_info_radix2()"

Return the single "radix" parameter hashref from the info above. This can be used when a subclass wants the radix parameter and other parameters too,

    package Math::PlanePath::MySubclass;
    use constant parameter_info_array =>
      [
       { name            => 'something_else',
         type            => 'integer',
         default         => '123',
       },
       Math::PlanePath::Base::Digits::parameter_info_radix2(),
      ];
    

If the "description" part should be more specific or more detailed then it could be overridden with for example

   { %{Math::PlanePath::Base::Digits::parameter_info_radix2()},
     description => 'Radix, for both something and something.',
   },
    

This function is not exportable since it's meant for a one-off call in an initializer and so no need to import it for repeated use.

SEE ALSO¶

Math::PlanePath, Math::PlanePath::Base::Generic Math::BigInt

HOME PAGE¶

<http://user42.tuxfamily.org/math-planepath/index.html>

LICENSE¶

Copyright 2010, 2011, 2012, 2013, 2014 Kevin Ryde This file is part of Math-PlanePath. Math-PlanePath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. Math-PlanePath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with Math-PlanePath. If not, see <http://www.gnu.org/licenses/>.