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, $exponent) = round_up_pow ($n, $radix)"
       "($power, $exponent) = round_down_pow ($n, $radix)"
           Return the power of $radix equal to or either higher or lower than $n.  For example

              ($pow, $exp) = round_down_pow (260, 2);
              # $pow==512  # the next higher power
              # $exp==9    # the exponent in that power
              # 2**9=512 is next above 260

              ($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, 2015, 2016, 2017, 2018, 2019, 2020 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/>.