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4d47's solution

to Robot Name in the Perl 6 Track

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Instructions
Test suite
Solution

Manage robot factory settings.

When robots come off the factory floor, they have no name.

The first time you boot them up, a random name is generated in the format of two uppercase letters followed by three digits, such as RX837 or BC811.

Every once in a while we need to reset a robot to its factory settings, which means that their name gets wiped. The next time you ask, it will respond with a new random name.

The names must be random: they should not follow a predictable sequence. Random names means a risk of collisions. Your solution must ensure that every existing robot has a unique name.

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 debugging session with Paul Blackwell at gSchool. http://gschool.it

Submitting Incomplete Solutions

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

robot-name.t

#!/usr/bin/env perl6
use v6;
use Test;
use lib $?FILE.IO.dirname;
use Robot;
plan 7;

subtest 'Class methods', {
  can-ok Robot, $_ for <name reset-name>;
}

srand 1;
my $robot = Robot.?new;
my Str $name = $robot.?name;
like $name, /^^<[A..Z]>**2 <[0..9]>**3$$/, 'Name matches schema';

srand 2;
is $robot.?name, $name, 'Name is persistent';
srand 1;
isnt Robot.new.?name, $name, 'New Robot cannot claim previous Robot name';

srand 1;
$robot.?reset-name;
$robot.?reset_name; # Allows next test to still pass for older solutions

isnt $robot.?name, $name, "'reset-name' cannot use previous Robot name";

diag "\nCreating 100 robots...";
push my @names, Robot.new.name for 1..100;
is @names, @names.unique, 'All names are unique';
subtest 'Randomness', {
  plan 2;
  isnt @names, @names.sort, 'Names not ordered';
  isnt @names, @names.sort.reverse, 'Names not reverse ordered';
}
unit class Robot;

my SetHash $names .= new;

has Str $.name = self.reset_name;

method reset_name {
    repeat {
        $!name = self!pick_name;
    } while $!name ∈ $names;
    $names{$!name} = True;
    $!name
}

method !pick_name {
    join '', ('A'..'Z').pick(2), (0..9).pick(3)
}

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?