($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 (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.

   @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.

    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).',
      }
    ]
    

    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.