# 4d47's solution

## to Trinary in the Perl 6 Track

Published at Jul 13 2018 · 0 comments
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 `prove6 .` in the exercise directory.

## 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 learned 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?