Avatar of 4d47
0
1
Genius
0
0

4d47's solution

to Trinary in the Perl 6 Track

Instructions
Test suite
Solution

Convert a trinary number, represented as a string (e.g. '102012'), to its decimal equivalent using first principles.

The program should consider strings specifying an invalid trinary as the value 0.

Trinary numbers contain three symbols: 0, 1, and 2.

The last place in a trinary number is the 1's place. The second to last is the 3's place, the third to last is the 9's place, etc.

# "102012"
    1       0       2       0       1       2    # the number
1*3^5 + 0*3^4 + 2*3^3 + 0*3^2 + 1*3^1 + 2*3^0    # the value
  243 +     0 +    54 +     0 +     3 +     2 =  302

If your language provides a method in the standard library to perform the conversion, pretend it doesn't exist and implement it yourself.

Resources

Remember to check out the Perl 6 documentation and resources pages for information, tips, and examples if you get stuck.

Running the tests

There is a test suite and module included with the exercise. The test suite (a file with the extension .t) will attempt to run routines from the module (a file with the extension .pm6). Add/modify routines in the module so that the tests will pass! You can view the test data by executing the command perl6 --doc *.t (* being the name of the test suite), and run the test suite for the exercise by executing the command prove . --exec=perl6 in the exercise directory. You can also add the -v flag e.g. prove . --exec=perl6 -v to display all tests, including any optional tests marked as 'TODO'.

Source

All of Computer Science http://www.wolframalpha.com/input/?i=binary&a=*C.binary-_*MathWorld-

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

trinary.t

#!/usr/bin/env perl6

use Test;
use lib $?FILE.IO.dirname;
use Trinary;

my @cases = (
    {
        input    => 1,
        expected => 1,
    },
    {
        input    => 2,
        expected => 2,
    },
    {
        input    => 10,
        expected => 3,
    },
    {
        input    => 11,
        expected => 4,
    },
    {
        input    => 100,
        expected => 9,
    },
    {
        input    => 10,
        expected => 3,
    },
    {
        input    => 112,
        expected => 14,
    },
    {
        input    => 222,
        expected => 26,
    },
    {
        input    => 1122000120,
        expected => 32091,
    },
    {
        input    => "carrot",
        expected => 0,
    }
);

plan @cases.elems;

is to-decimal( .<input> ), .<expected>, .<input> for @cases;
sub to-decimal(Str(Cool) $input) is export {
    return 0 unless $input ~~ /^<[012]>+$/;
    $input.comb.reduce: { 3 * $^a + $^b }
}

What can you learn from this solution?

A huge amount can be learnt from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that I could read more about to develop my understanding?