I look forward to the weekly challenges only to learn something new in Raku. I would like to thank many people (unfair to name few here) who guided me every time I am stuck, thanks to the Gang at Twitter.
As the pattern I always follow, I started with Perl solution. I would not waste any time explaining my code as it is self explanatory.
PERL
Task #1: Stepping Numbers
#!/usr/bin/perl
use strict;
use warnings;
my $start = $ARGV[0] || 100;
my $stop = $ARGV[1] || 999;
die "ERROR: Invalid start number [$start]\n"
unless ($start >= 100 &&
$start <= 999);
die "ERROR: Invalid stop number [$stop]\n"
unless ($start <= $stop &&
$stop >= 100 &&
$stop <= 999);
while ($start <= $stop) {
my ($d1, $d2, $d3) = split //, $start, 3;
if ( ((($d1 - $d2) == 1) && (($d2 - $d3) == 1))
|| ((($d2 - $d1) == 1) && (($d3 - $d2) == 1)) ) {
print "$start\n";
}
$start++;
}
Task #2: Lucky Winner
This was my favourite of the two tasks. In my first draft, I decided to let Machine picks the coin first. But later I found out after checking out E. Choroba solution, the first player has advantage other the second player. Later I was reading the blog by fellow Team PWC, member Cheok-Yin Fung and read the comment by Toby Inskter that whoever picks £2 coin first is the winner. He even suggested that there should be multiple coins to make it even more challenging. However, it was too late to make any changes to the task, I decided to focus on what is required as of now.
I implemented the random selection of player as suggested by E. Choroba.
my $current = int rand(2);
I also declared hashref $coins to keep the coins collected and total amount in the bank for each player.
my $coins = {
100 => "£1", 50 => "50p", 1 => "1p", 10 => "10p",
5 => "5p", 20 => "20p", 200 => "£2", 2 => "2p" ,
};
Rest of code is just straight forward, nothing great about it.
#!/usr/bin/perl
use strict;
use warnings;
my $coins = {
100 => "£1", 50 => "50p", 1 => "1p", 10 => "10p",
5 => "5p", 20 => "20p", 200 => "£2", 2 => "2p" ,
};
my $table = [ keys %$coins ];
my $players = {
0 => { "name" => "Human", "bank" => 0, "coins" => [] },
1 => { "name" => "Machine", "bank" => 0, "coins" => [] },
};
# Pick random player 0 or 1.
# DISCLAIMER:
# E. Choroba found out the player who picks the coin
# first is always the winner.
my $current = int rand(2);
my $coin;
while ($#$table) {
if ($table->[0] > $table->[-1]) {
$coin = shift @$table;
}
else {
$coin = pop @$table;
}
$players->{$current}->{bank} += $coin;
push @{$players->{$current}->{coins}}, $coins->{$coin};
$current = ($current)?(0):(1);
}
$coin = shift @$table;
$players->{$current}->{bank} += $coin;
push @{$players->{$current}->{coins}}, $coins->{$coin};
_declare_lucky_winner($players);
_show_coins($players);
The handy sub _declare_winner() and sub _show_coins() as below:
sub _declare_lucky_winner {
my ($players) = @_;
print "The lucky winner is ";
if ($players->{0}->{bank} > $players->{1}->{bank}) {
print $players->{0}->{name};
}
else {
print $players->{1}->{name};
}
print ".\n";
}
sub _show_coins {
my ($players) = @_;
foreach (0..1) {
print sprintf("%s picked coins %s.\n",
$players->{$_}->{name}, join(", ", @{$players->{$_}->{coins}}) );
}
}
RAKU
Task #1: Stepping Numbers
Now it is time to get serious and focus. One of my favourite routine comb() of Raku came very handy in this task. As per my understanding, it works like split() in Perl. I also used Zip metaoperator and Reduction metaoperator in this task.
With the above handy routine and metaoperators, I was ready to formulate my logic and came up with this:
([==] $start.comb("") Z- <0 1 2>);
Lets follow the sequence, in my humble opinion, $start.comb(""), would split the 3 digits number into individual digit. After that we apply Zip metaoperator (Z-) with <0 1 2>. What this effectively doing is something like below:
<first digit> - 0
<second digit> - 1
<third digit> - 2
and returns 3 numbers at the end. Finally applying Reduction metaoperator, [==] to the end result.
Just to explain, the [==] is basically doing this and return true or false:
<first digit> == <second digit> == <third digit>
Here is the final version:
#!/usr/bin/env perl6
use v6.c;
sub MAIN(Int $start is copy = 100, Int $stop = 999) {
die "ERROR: Invalid start [$start]." if $start < 100;
die "ERROR: Invalid stop [$stop]." if $stop > 999 || $stop < $start;
while $start <= $stop {
say $start if ([==] $start.comb("") Z- <0 1 2>)
||
([==] $start.comb("") Z- <2 1 0>);
$start++;
}
}
Task #2: Lucky Winner
As I said above, this task was my favourite and it gave me lots of opportunity to learn new things in Raku. I will go through every bit in it just to remind myself so that I don’t forget next time.
I noticed, defining hash doesn’t need braces. For example, in Perl, I always do something like below:
my %hash = ( 1 => "a", 2 => "b", 3 => "c"3 );
but in Raku, I can do something like this to define all the coins used in this task:
my %coins =
100 => "£1", 50 => "50p", 1 => "1p", 10 => "10p",
5 => "5p", 20 => "20p", 200 => "£2", 2 => "2p"
;
Now I wanted to create a list of keys of the hash %coins.
So this is what I did.
my @table = ();
for %coins.keys -> $c {
push @table, $c;
}
Now time to mix up the coins in the list, so it arranges the coins in random order every time.
I used routine pick to ramdomize the elements in the list.
@table = @table.pick(@table);
The best finding of this task to figure out how find random number between 0 and 1.
This is what I found on the web using the routine pick.
my Int $current = (^2).pick;
Another find in my fight today, to find the last member of array, we do $array[-1] in Perl, right?
However, in Raku, it is completely out of this world, @array[*-1].
Rest is as usual stuff and the final version is as below:
#!/usr/bin/env perl6
use v6.c;
sub MAIN() {
# Setup coins with description
my %coins =
100 => "£1", 50 => "50p", 1 => "1p", 10 => "10p",
5 => "5p", 20 => "20p", 200 => "£2", 2 => "2p"
;
# Arrange coins on the table
my @table = ();
for %coins.keys -> $c {
push @table, $c;
}
@table = @table.pick(@table);
# Setup players for the game
my %players =
0 => { "name" => "Human", "bank" => 0, "coins" => [] },
1 => { "name" => "Machine", "bank" => 0, "coins" => [] },
;
# Pick random player 0 or 1.
# DISCLAIMER:
# E. Choroba found out the player who picks the coin
# first is always the winner.
my Int $current = (^2).pick;
# Play the game now
my $coin;
while @table.elems {
if @table[0] > @table[*-1] {
$coin = @table.shift;
}
else {
$coin = @table.pop;
}
%players{$current}<"bank"> += $coin;
%players{$current}<"coins">.append(%coins{$coin});
$current = ($current)??(0)!!(1);
}
declare-lucky-winner(%players);
show-coins(%players);
}
sub declare-lucky-winner(%players) {
if %players<0><"bank"> > %players<1><"bank"> {
say "The lucky winner is " ~ %players<0><name> ~ ".";
}
else {
say "The lucky winner is " ~ %players<1><name> ~ ".";
}
}
sub show-coins(%players) {
for 0..1 -> $player {
say %players{$player}<name> ~ " picked coins " ~
@(%players{$player}<"coins">).join(", ") ~ ".";
}
}
That’s it for this week. Speak to you soon.