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4d47's solution

to Raindrops in the Perl 6 Track

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Instructions
Test suite
Solution

Convert a number to a string, the contents of which depend on the number's factors.

  • If the number has 3 as a factor, output 'Pling'.
  • If the number has 5 as a factor, output 'Plang'.
  • If the number has 7 as a factor, output 'Plong'.
  • If the number does not have 3, 5, or 7 as a factor, just pass the number's digits straight through.

Examples

  • 28's factors are 1, 2, 4, 7, 14, 28.
    • In raindrop-speak, this would be a simple "Plong".
  • 30's factors are 1, 2, 3, 5, 6, 10, 15, 30.
    • In raindrop-speak, this would be a "PlingPlang".
  • 34 has four factors: 1, 2, 17, and 34.
    • In raindrop-speak, this would be "34".

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

A variation on a famous interview question intended to weed out potential candidates. http://jumpstartlab.com

Submitting Incomplete Solutions

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

raindrops.t

#!/usr/bin/env perl6
use v6;
use Test;
use JSON::Fast;
use lib $?FILE.IO.dirname;
use Raindrops;
plan 18;

my $c-data = from-json $=pod.pop.contents;
for @($c-data<cases>) {
  subtest {
    plan 2;
    is .<input><number>.&raindrop, |.<expected description>;
    isa-ok .<input><number>.&raindrop, Str;
  }
}

=head2 Canonical Data
=begin code
{
  "exercise": "raindrops",
  "version": "1.1.0",
  "cases": [
    {
      "description": "the sound for 1 is 1",
      "property": "convert",
      "input": {
        "number": 1
      },
      "expected": "1"
    },
    {
      "description": "the sound for 3 is Pling",
      "property": "convert",
      "input": {
        "number": 3
      },
      "expected": "Pling"
    },
    {
      "description": "the sound for 5 is Plang",
      "property": "convert",
      "input": {
        "number": 5
      },
      "expected": "Plang"
    },
    {
      "description": "the sound for 7 is Plong",
      "property": "convert",
      "input": {
        "number": 7
      },
      "expected": "Plong"
    },
    {
      "description": "the sound for 6 is Pling as it has a factor 3",
      "property": "convert",
      "input": {
        "number": 6
      },
      "expected": "Pling"
    },
    {
      "description": "2 to the power 3 does not make a raindrop sound as 3 is the exponent not the base",
      "property": "convert",
      "input": {
        "number": 8
      },
      "expected": "8"
    },
    {
      "description": "the sound for 9 is Pling as it has a factor 3",
      "property": "convert",
      "input": {
        "number": 9
      },
      "expected": "Pling"
    },
    {
      "description": "the sound for 10 is Plang as it has a factor 5",
      "property": "convert",
      "input": {
        "number": 10
      },
      "expected": "Plang"
    },
    {
      "description": "the sound for 14 is Plong as it has a factor of 7",
      "property": "convert",
      "input": {
        "number": 14
      },
      "expected": "Plong"
    },
    {
      "description": "the sound for 15 is PlingPlang as it has factors 3 and 5",
      "property": "convert",
      "input": {
        "number": 15
      },
      "expected": "PlingPlang"
    },
    {
      "description": "the sound for 21 is PlingPlong as it has factors 3 and 7",
      "property": "convert",
      "input": {
        "number": 21
      },
      "expected": "PlingPlong"
    },
    {
      "description": "the sound for 25 is Plang as it has a factor 5",
      "property": "convert",
      "input": {
        "number": 25
      },
      "expected": "Plang"
    },
    {
      "description": "the sound for 27 is Pling as it has a factor 3",
      "property": "convert",
      "input": {
        "number": 27
      },
      "expected": "Pling"
    },
    {
      "description": "the sound for 35 is PlangPlong as it has factors 5 and 7",
      "property": "convert",
      "input": {
        "number": 35
      },
      "expected": "PlangPlong"
    },
    {
      "description": "the sound for 49 is Plong as it has a factor 7",
      "property": "convert",
      "input": {
        "number": 49
      },
      "expected": "Plong"
    },
    {
      "description": "the sound for 52 is 52",
      "property": "convert",
      "input": {
        "number": 52
      },
      "expected": "52"
    },
    {
      "description": "the sound for 105 is PlingPlangPlong as it has factors 3, 5 and 7",
      "property": "convert",
      "input": {
        "number": 105
      },
      "expected": "PlingPlangPlong"
    },
    {
      "description": "the sound for 3125 is Plang as it has a factor 5",
      "property": "convert",
      "input": {
        "number": 3125
      },
      "expected": "Plang"
    }
  ]
}
=end code
unit class Raindrops;

method convert(UInt $n --> Cool) {
    # 'is cached' on methods not yet implemented.
    my $output = '';
    $output ~= 'Pling' if $n %% 3;
    $output ~= 'Plang' if $n %% 5;
    $output ~= 'Plong' if $n %% 7;
    $output || $n
}

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?