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4d47's solution

to Hello World in the Perl 6 Track

Test suite

The classical introductory exercise. Just say "Hello, World!".

"Hello, World!" is the traditional first program for beginning programming in a new language or environment.

The objectives are simple:

  • Write a function that returns the string "Hello, World!".
  • Run the test suite and make sure that it succeeds.
  • Submit your solution and check it at the website.

If everything goes well, you will be ready to fetch your first real exercise.


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'.


This is an exercise to introduce users to using Exercism http://en.wikipedia.org/wiki/%22Hello,_world!%22_program

Submitting Incomplete Solutions

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


#!/usr/bin/env perl6
use v6;
use Test;
use JSON::Fast;
use lib $?FILE.IO.dirname; #`[Look for the module inside the same directory as this test file.]
use HelloWorld;
plan 1; #`[This is how many tests we expect to run.]

my Version:D $version = v3; #`[The version we will be matching against the exercise.]

#`[If the exercise is updated, we want to make sure other people testing
your code don't think you've made a mistake if things have changed!]
if HelloWorld.^ver !~~ $version {
  warn "\nExercise version mismatch. Further tests may fail!"
    ~ "\nHelloWorld is {HelloWorld.^ver.gist}. "
    ~ "Test is {$version.gist}.\n";

my $c-data = from-json $=pod.pop.contents;
# Go through the cases and check that &hello gives us the correct response.
is hello, |.<expected description> for @($c-data<cases>);

=head2 Canonical Data
=begin code
  "exercise": "hello-world",
  "version": "1.1.0",
  "cases": [
      "description": "Say Hi!",
      "property": "hello",
      "input": {},
      "expected": "Hello, World!"
=end code
unit module HelloWorld:ver<1>;

sub hello(Str $name? --> Str) is export {
    "Hello, {$name || 'World'}!"

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?

Community comments

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over 1 year ago
4d47 says

Remove default value on optional param, thanks @mienaikageb :)