---
layout: language-war
date: 2018-10-11
title: "Hackerrank solutions: Python 3 and Perl 6 (part 2)"
tags:
- Hackerrank
- Perl6
- Python
- Python3
- Programming
- Raku
---

{% markdown %}
# Hackerrank solutions: Python 3 and Perl 6 (part 2)
{% endmarkdown %}

{% markdown %}
As a continuation of the [previous
part](/post/2018/09/13/hackerrank-solutions-python3-and-perl6-part-1/) of this
series, I will be continuing to work through some Hackerrank challenges for
Python 3, and compare the solutions to how I would solve them in a language I'm
more proficient in, Perl 6. In this post, I will work through some of the
Python 3 string challenges from Hackerrank.

Raiph [posted a comment on
Reddit](https://www.reddit.com/r/perl6/comments/9ffc2p/hackerrank_solutions_python_3_and_perl_6_part_1/e5xml3m)
suggesting a slightly different layout, which I will be using for this post.
Additional comments are always welcome as I try to improve the format.
{% endmarkdown %}

{% admonition_md Disclaimer %}
Once again I'd like to make clear I'm trying to stick to the original
Hackerrank challenges by not using any imports not specifically used in the
original challenge. If you have suggestions for Python 3 or Perl 6 modules to
make a given task easier, I still appreciate them, but I won't update my
solutions to use a module.
{% endadmonition_md %}

{% markdown %}
## Challenges
{% endmarkdown %}

<div class="language-war">
    <div class="language-announcer">

{% markdown %}
### String Split and Join

This challenge involves a string containing spaces, where the spaces are to be
replaced with dashes (`-`) instead.
{% endmarkdown %}

    </div>
    <div class="language-arena">
        <div class="language-challenger">
            <div class="language-code">

{% highlight python3 tio=https://tio.run/##K6gsycjPM/7/PyU1TaG4ICezJD4xLyU@Kz8zTyMnMy9V04pLAQiKUktKi/IUlHSV9OBSemDlGkoKSpqa/wuKMvNKNNAMyMwrKC3R0ARKp@XnKyQlFgFxFQA %}
def split_and_join(line):
    return "-".join(line.split(" "))
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
I personally am not too fond that `join` takes a list of words to join
together, whereas `split` takes a word to split with. It feels a little
inconsistent. It also doesn't allow me to read the code logically from left to
right.
{% endmarkdown %}

            </div>
        </div>
        <div class="language-defender">
            <div class="language-code">

{% highlight perl6 tio=https://tio.run/##K0gtyjH7/7@4NEmhuCAns0Q3MS9FNys/M09BQyUnMy9VU6GaSwEIwBw9sBINJQUlTT2QGg0lXSVNrtr/KlqefnrFOaVFBXpqqKboFSdW/k/Lz1dISiwC4ioA %}
sub split-and-join ($line) {
    $line.split(" ").join("-")
}
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
The Perl 6 solution to the challenge does the same as the Python variant. Even
the function names are the same! The biggest difference is that I can chain the
functions from left to right, leading to clearer code.
{% endmarkdown %}

            </div>
        </div>
    </div>
    <div class="language-announcer">

{% markdown %}
### What's Your Name?

The next challenge is a simply string formatting task. You get two inputs, a
first name and a last name, and have to put it in a string which will be
printed to `STDOUT`.
{% endmarkdown %}

    </div>
    <div class="language-arena">
        <div class="language-challenger">
            <div class="language-code">

{% highlight python3 tio=https://tio.run/##XYzBCsIwEETv/YqxUEigePHmD@jZm6cSyRYj22ww2UK/PobqyWEOAzPz0laeEk@1epqR3iGWaVbmKbqFjBvxsOcOTXtl@isxC4bcfMBdFC/NBZ54JY@2EKQdeOwx4Pu39R8bYtJi7IhfsPWiwUu3uoib5KzLBw %}
def print_full_name(a, b):
    print("Hello %s %s! You just delved into python." % (a, b))
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
Before you begin, I know this can be done using `f""` strings, and that was my
first attempt to use as well. However, Hackerrank did not accept this,
complaining about invalid syntax, so I assume they're running an older Python 3
than I do.

That said, this is a simple `printf` formatted string, which then accepts a
tuple of arguments to put into the string. `printf` formatted string are very
powerful in their possibilities, and it's clear to read.
{% endmarkdown %}

            </div>
        </div>
        <div class="language-defender">
            <div class="language-code">

{% highlight perl6 tio=https://tio.run/##K0gtyjH7/7@4NEmhoCgzr0Q3rTQnRzcvMTdVQyVRR0ElSVOhmksBCIoTKxWUPFJzcvIVVBKB4ooKkfmlClmlxSUKKak5ZakpCkDd@QoBQPMUzPSUuGr/Y5in5emnl55aAjQVytL875NYVFTJFZ6YkwMA %}
sub print-full-name($a, $b) {
    say "Hello $a $b! You just delved into Perl 6."
}
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
Perl 6 has double-quote semantics that many people may be familiar with from
other languages. When you insert a variable in a double-quoted string, it's
`.Str` value will be used. That is to say, the value will be converted to a
`Str` if required, and then put into the string.

If you need it or want it for clarity, you can also use `"Hello {$a}"` in Perl
6, allowing you to use it similarly to Python 3's `f""` strings.
{% endmarkdown %}

            </div>
        </div>
    </div>
    <div class="language-announcer">

{% markdown %}
### Mutations

You are given a string _string_, an integer _position_ and a character
_character_. In _string_, replace the character at _position_ to the given
_character_. The position is counted from starting point 0, so I don't have to
think about differences between what a human or computer considers to be
position 1 in a string.
{% endmarkdown %}

    </div>
    <div class="language-arena">
        <div class="language-challenger">
            <div class="language-code">

{% highlight python3 tio=https://tio.run/##VY5BC8IwDIXv/RVhpxaKIN4Ef4mIjNm5iCYlTQ/79bXrpmIuyeN975E468R0KOUWRnhl7TVckwrS3a7LQ@SEikwehqmXftAg7migzqITnOCJSTfc/YzzJ3ipyDdqGiBBsxB03e7BSLbxrsTaoPb/C6SY1ToPi7WJptbLlZHZ7I28AQ %}
def mutate_string(string, position, character):
    chars = list(string)
    chars[position] = character

    return "".join(chars)
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
This is basically what the example showed as well that came with the challenge,
so wasn't too hard to solve. My only complaint was that I couldn't call my list
"list", because that's a reserved keyword.
{% endmarkdown %}

            </div>
        </div>
        <div class="language-defender">
            <div class="language-code">

{% highlight perl6 tio=https://tio.run/##K0gtyjH7/7@4NEkht7QksSRVt7ikKDMvXUFDBcLQUVApyC/OLMnMzwMykzMSixKTS1KLNBWquRSAILdSwSEns7hEwVYBqkEvOT83yRosCZaJhuuPBSmCm2DNhVCjl5WfmWfNVfsfxQ0aKlqefnrpqSVAizFYmnrFiZX/0/LzuQy5igA %}
sub mutate-string ($string, $position, $character) {
    my @list = $string.comb;
    @list[$position] = $character;

    @list.join;
}
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
The Perl 6 variant does the same things as the Python variant. `comb` without
arguments converts a string to a list of characters, and `join` without
arguments joins a list together to a string.
{% endmarkdown %}

            </div>
        </div>
    </div>
    <div class="language-announcer">

{% markdown %}
### Find a String

In the following challenge you are given a string _string_, and a substring
_sub\_string_. The challenge is to find how often a substring occurs in the
_string_. The substrings may overlap one another, so the string `"ABCDCDC"`
contains the substring `"CDC"` twice.
{% endmarkdown %}

    </div>
    <div class="language-arena">
        <div class="language-challenger">
            <div class="language-code">

{% highlight python3 tio=https://tio.run/##XU67CsMwDNz9FTfaxENKt4CHPv4ilNCHkwqKbBx76Ne7bhxIqYSQdNzp5N/x6Xif88OOuLvEcZjTbY6BeJK1aRRkqLPqBEosRBi0YllHF0AgRrjyZGWr8bK8qtUq@QaNqGBPHaGprO32Bcb8eG26zbIx2FXPYGMKXOHsCz/K//eJfYpSaayDUvlwPJ1LilIf %}
def count_substring(string, sub_string):
    count = 0

    for i in range(0, len(string)):
        if string[i:i + len(sub_string)] == sub_string:
            count += 1

    return count
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
As solution to this challenge I loop through the entire _string_, and check
whether it contains the _sub\_string_ at that point. If it does, I increment
_count_ by 1. Now, I learned that Python also has the inline `if`, just like
Perl 6 does, however, it also *needs* an `else` block. That put me off from
using it in this situation. I think it puts me off from using it in most
situations, actually. With an `else` coming after it, it just becomes messy to
read, in my opinion.
{% endmarkdown %}

            </div>
        </div>
        <div class="language-defender">
            <div class="language-code">

{% highlight perl6
tio=https://tio.run/##K0gtyjH7/7@4NEkhOb80r0QXyCouKcrMS1fQUIEwdBRUgIK6EI6mQjUXZ2pOam6xAlRaoa5OIdcqvwxoUGKBPpJSfa7a/2hmaqhoefrppaeWAM2EsjT1ihMr/zs6ObsAIRcQAwA %}
sub count-substring ($string, $sub-string) {
    elems $string ~~ m:overlap/$sub-string/
}
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
The Perl 6 version makes use of some regex magic, and the `elems` subroutine.
`elems` returns the number of elements in a list, which in this case would be
the number of matches found by the regex. The `m:overlap//` makes a regex to
*m*atch, with *overlap*ping strings.
{% endmarkdown %}

            </div>
        </div>
    </div>
    <div class="language-announcer">

{% markdown %}
### String Validators

In the following challenge, the program is given a string _s_, and have to
validate a number of properties on this string. These are, in order, whether
they contain

- alphanumeric characters (a-z, A-Z or 0-9),
- alphabetic characters (a-z or A-Z),
- digits (0-9),
- lowercase characters (a-z),
- uppercase characters (A-Z).

If any character in the given string passes a validation, it must print
`"True"`, otherwise it must print `"False"`.

{% endmarkdown %}

    </div>
    <div class="language-arena">
        <div class="language-challenger">
            <div class="language-code">

{% highlight python3 tio=https://tio.run/##hZLNioMwEIDvPsXQPdTAIrS9CR72sk@wt1JCVtMaqklIIqWUPrubn6p1MZib38x8zmQi76YW/ND37AwYc9JSjKEoYItxSxjHeJsnYI@GAhiXnUlR4kFZ0/Lq6MN/urMhDe/aTQ7fpNH0853Lmizwil2YWeCNuFG1wDspJ@7xMzRzFso2RJRtERqmTapRPpbZybgwr4aPryZPQHjlazKmPUrfSqYBp/wCflRHk7jWzfhPa1FcG/JXtOGKZlqPYtohf0Ubbnim9SimHfJXtGFBM61HMe2QH7QQvFd6d@/K7zEkZg6lCI3hTAs1vkS3fAvd7l1s@pNUjA@Kow2dUN9//ZbVbn/4@AM %}
if __name__ == '__main__':
    s = input()

    checks = {
        "alnum": False,
        "alpha": False,
        "digit": False,
        "lower": False,
        "upper": False
    }

    for char in list(s):
        if not checks["alnum"] and char.isalnum():
            checks["alnum"] = True

        if not checks["alpha"] and char.isalpha():
            checks["alpha"] = True

        if not checks["digit"] and char.isdigit():
            checks["digit"] = True

        if not checks["lower"] and char.islower():
            checks["lower"] = True

        if not checks["upper"] and char.isupper():
            checks["upper"] = True 

    keys = list(checks.keys())
    keys.sort()

    for key in keys:
        print(checks[key])
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
As stated in the disclaimer, I don't want to make use of any `import`
statements unless these are explicitly given in the original challenges. This
means I can't use regexes, as these are stuffed away in the `re` packages in
Python. Luckily, Python has the correct check available as a method on the
string object, so I can still check them in a single line.

I first tried to call the methods on _s_ directly, but this seemed to require
the entire string to match the check, instead of just any character in the
string. So I had to loop through the string by character, which I did. If any
character is found to validate, the appropriate key in the _checks_ dict will
be set to `True`. Once I've walked through the entire string, I sort the _keys_
from _checks_ so I can be sure they're printed in the right order.
{% endmarkdown %}

            </div>
        </div>
        <div class="language-defender">
            <div class="language-code">

{% highlight perl6
tio=https://tio.run/##K0gtyjH7/7@4NEnB19HTT6GaSwEIcisVVIoVbBVUtDz99NJTS6y5wMLFiZUKxfkgqbo6BX2bxJy80lw7fWvscgUZiTjkUjLTM0twyOXkl6cW4ZArLSiAyNX@/@@YlJxiaGSsDAA %}
sub MAIN {
    my $s = $*IN.get;

    say so $s ~~ /<alnum>/;
    say so $s ~~ /<alpha>/;
    say so $s ~~ /<digit>/;
    say so $s ~~ /<lower>/;
    say so $s ~~ /<upper>/;
}
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
Perl 6 does have regexes available in the main namespace by default, so that
made this challenge a lot easier to work with. `$*IN` in a special variable
that refers to `STDIN`, and the `.slurp` method reads all remaining data from
the buffer.

The next 5 lines all do a `say`, which acts like `print` in Python 3. The `so`
function coerces a value to become a `Bool`. When a `Bool` is given to `say`,
it will be coerced to a string representation again, and become either `"True"`
or `"False"`. The smartmatch operator `~~` has already been covered in the
previous post, so I recommend you read that as well if you haven't yet.

In Perl 6, regexes are (usually) delimited by the `/` character. The `<alnum>`,
`<alpha>` etcetera parts are [predefined character classes][classes] in Perl 6
regexes. These check for exactly what we need in the challenges, so were a good
pick to solve them.

[classes]: https://docs.perl6.org/language/regexes.html#Predefined_character_classes
{% endmarkdown %}

            </div>
        </div>
    </div>
    <div class="language-announcer">

{% markdown %}
### Text Wrap

You are given a string _s_ and a width _w_. The string should be split over
multiple lines so it is never more wide than _w_.
{% endmarkdown %}

    </div>
    <div class="language-arena">
        <div class="language-challenger">
            <div class="language-code">

{% highlight python3 tio=https://tio.run/##K6gsycjPM/7/PzO3IL@oRKEktaKkvCixgIsrJTVNAcTSKC4pysxL11HITayIL89MKcnQtOJSAIKi1JLSojwFpZg8Jb2s/Mw8DZhePRzaNP8XAIVKNMDSmXkFpSUamjoKIBEoBwj@Ozo5u7i6uXt4enn7@Pr5BwQGBYeEhoVHREZxmQIA %}
import textwrap

def wrap(string, max_width):
    return "\n".join(textwrap.wrap(string, max_width))
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
This challenge introduces the first Python module: `textwrap`. This makes the
challenge very easy to solve as well, using the `wrap` function exposed by the
module. This function makes a list of strings, each no longer than the given
width. I then join these together with newlines to get the desired output.
{% endmarkdown %}

            </div>
        </div>
        <div class="language-defender">
            <div class="language-code">

{% highlight perl6 tio=https://tio.run/##K0gtyjH7/7@4NEmhvCixQEFDpbikKDMvXUdBpTwzpSRDU6GaSwEIoMJ6yfm5SRpQKb2s/Mw8DaWYPCVNrtr/IO0aKlqefnrpqSVA7VCWnmdeiaZecWLlf0cnZxdXN3cPTy9vH18//4DAoOCQ0LDwiMgoLlMA %}
sub wrap ($string, $width) {
    $string.comb($width).join("\n")
}
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
For the Perl 6 solution, I have not used an additional module, as all the
functionality are in the core namespace. I actually made a module in Perl 6 for
a less primitive wrapping functionality, called [`String::Fold`][string::fold].

In this solution, I use `comb` with the `$width` argument. This returns a list
of strings, each no longer than the given width, just like Python's
`textwrap.wrap`. I can then join these together with newlines as well to get
the same result.

[string::fold]: https://modules.perl6.org/dist/String::Fold:cpan:TYIL
{% endmarkdown %}

            </div>
        </div>
    </div>
    <div class="language-announcer">

{% markdown %}
### Designer Door Mat

This challenge is more complex than previous challenges. The task at hand is to
"draw" a certain "design" as the output. For the input, you are given both a
height _y_ and a width _x_, however _x_ must always be _y_ × 3, so you can
ignore the second argument.

This one is much simpler to explain using two examples. The first example is
the output if the input were `7 21`.
{% endmarkdown %}

{% highlight text %}
---------.|.---------
------.|..|..|.------
---.|..|..|..|..|.---
-------WELCOME-------
---.|..|..|..|..|.---
------.|..|..|.------
---------.|.---------
{% endhighlight %}

{% markdown %}
In the second example, the input is `11 33`.
{% endmarkdown %}

{% highlight text %}
---------------.|.---------------
------------.|..|..|.------------
---------.|..|..|..|..|.---------
------.|..|..|..|..|..|..|.------
---.|..|..|..|..|..|..|..|..|.---
-------------WELCOME-------------
---.|..|..|..|..|..|..|..|..|.---
------.|..|..|..|..|..|..|.------
---------.|..|..|..|..|.---------
------------.|..|..|.------------
---------------.|.---------------
{% endhighlight %}

    </div>
    <div class="language-arena">
        <div class="language-challenger">
            <div class="language-code">

{% highlight python3 tio=https://tio.run/##zZDNS8MwGMbv@SseMwbJlrbrehCEnWS3DS@CBxGpNFsCJQ1p5xD832s@Nh2I7GpyCHmf3/u8H/ZjUJ2pxnFyg@LQu@JNm0Kad9gkEKKk3qsBK2gzMKaNPQyM571ttX/58@KFk6NuBuWJEzpDRVTd7s45p3CGkqPAkhMywWNnERiy6xxabaRH4Wqzl6wUUcHc83cE/pjOvDZ1r2TvLRmL@MwbRctIfKuxYOonA7tI9E3xc/mQYV1A6bQPl2IKRjPqqYQL0PwzD/8fCx@7IHgcY6ubppVxAPLbMRZKSSxoqa8idV5xkfSn9eb@Ybum4gpOUslNd5Tur92FsMBCIPvfuxvHWyzLLw %}
#! /usr/bin/env python3

height = int((input().split())[0])
width = height * 3
half = int((height - 1) / 2)

# Top half
for line in range(1, half + 1):
    non_dashes = ((line * 2) - 1)
    dashes = int((width - (non_dashes * 3)) / 2)

    print("%s%s%s" % ("-" * dashes, ".|." * non_dashes, "-" * dashes))

# Middle line
print("%s%s%s" % (
    "-" * (int(width / 2) - 3),
    "WELCOME",
    "-" * (int(width / 2) - 3)
))

# Lower half
for line in range(half, 0, -1):
    non_dashes = ((line * 2) - 1)
    dashes = int((width - (non_dashes * 3)) / 2)

    print("%s%s%s" % ("-" * dashes, ".|." * non_dashes, "-" * dashes))
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
I split the code up in a top half, middle line and lower half, to make it
easier to reason about. The `for` loops contain some logic to get the right
output on every line. I found out that `range` supports a third argument,
allowing me to count down with it as well, which was perfect for this
situation.
{% endmarkdown %}

            </div>
        </div>
        <div class="language-defender">
            <div class="language-code">

{% highlight perl6 tio=https://tio.run/##zZBBTsMwEEX3PsXgdpEgxVFSqSwiVqiLSi1skFiiIE@xpeBEdtpQhZyDo3CAHix0UpKGSuzxypp5/8/XL9Bm87adXEG4dTZ80SZEs4OCxoy97WGqUL@qEm5her28Fy7b2kJUuZVOKEylWJoy6bhKy1IR9iM4fMLstFFptgkGG68HAoh8OHxBnDA2gce8AALZJrcQCfFLVTM4PvIyuQlk6hS6zuqZzsQ@eSUDM9qfQgXH30hIyfzhNKlcugde84DDey9vai4@RDc4S5sLhiesofBrLWWGkGmDbOzl9QnoFqWc@c3TYnX3sF7U8DfCu0ZWeYX23Il3UYovLO7QOvzX7bTtDcTRNw %}
#! /usr/bin/env perl6

my $height = $*IN.slurp.words.head.Int;
my $width = $height × 3;
my $half-height = ($height - 1) ÷ 2;

# Top half
for 1..$half-height {
    my $non-dashes = ($_ × 2) - 1;
    my $dashes = ($width - ($non-dashes × 3)) ÷ 2;

    say "{"-" x $dashes}{".|." x $non-dashes}{"-" x $dashes}";
}

# Middle line
say "{"-" x (($width ÷ 2) - 3)}WELCOME{ "-" x (($width ÷ 2) - 3)}";

# Lower half
for (1..$half-height).reverse {
    my $non-dashes = ($_ × 2) - 1;
    my $dashes = ($width - ($non-dashes × 3)) ÷ 2;

    say "{"-" x $dashes}{".|." x $non-dashes}{"-" x $dashes}";
}
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
As usual, the code is functionally the same. I must admit I like the functional
style to get an `Int` from the first argument much more than the way I do it in
Python, though.

A thing I learned is that the `..` operator that generates a sequence does not
have a way to make a sequence that counts down, so I had to use `.reverse` on a
sequence that counts up. I had expected this to Just Work as I expected and
count down if the left hand side would be larger than the right hand side.

You may notice some fancy Unicode characters in the source, namely `×` for
multiplication, and ÷ for division. Perl 6 allows Unicode characters in the
source files, which can oftentimes lead to prettier code. In this particular
instance, there's no big difference in code readability, though. And for those
who don't yet have a modern editor that can make Unicode characters, do not
worry, as the ASCII equivalents (`*` and `/` respectively) still work as well.
{% endmarkdown %}

            </div>
        </div>
    </div>
    <div class="language-announcer">

{% markdown %}
### String Formatting

In this challenge, you are to produce a table with four columns. The columns
should contain the decimal, octal, hexadecimal and binary values of the row
numbers. The function receives an int _number_. The table should contain that
many rows, starting with row number 1.
{% endmarkdown %}

    </div>
    <div class="language-arena">
        <div class="language-challenger">
            <div class="language-code">

{% highlight python3 tio=https://tio.run/##jZFNCoMwEIX3nmIQhIQG0XYn9CwSTawpJoYYqVJ6dht/W7uQDlll3vveTKJ7W9bqMgyMF6CNUDYtaiOptZwh1cqMG5x44ErSLn0IZku4QsUV8p9Rkr38cJavWuxNYncJAoQCQ9WNo5jA3IcTxAtvLMZzIWnliI72YQkcmnvbWLRl4s1S53Y1JPV/lpJ3dJeUdDtjqzU36ACQCUVNv3iz49DNND0m8oMG1uNDAGgZhMyLkO/hyBKE8fD7EyNKKN1ahF33HL0B %}
def print_formatted(number):
    max_width = len("{0:b}".format(number))

    for i in range(1, number + 1):
        decimal = "{0}".format(i).rjust(max_width)
        octal = "{0:o}".format(i).rjust(max_width)
        hexadecimal = "{0:x}".format(i).upper().rjust(max_width)
        binary = "{0:b}".format(i).rjust(max_width)

        print("%s %s %s %s" % (decimal, octal, hexadecimal, binary))
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
In the Python 3 solution I first calculate the max width I need to take into
account. Then I loop from 1 until _number_ to get the right amount of rows.
Each iteration, I format the number correctly, and then print it out using a
printf format string.

The hardest part of this challenge was to get formatting right the way
Hackerrank wanted it. But I guess that was the entire point of the challenge.
{% endmarkdown %}

            </div>
        </div>
        <div class="language-defender">
            <div class="language-code">

{% highlight perl6 tio=https://tio.run/##XY9NCsIwEIX3PcUQIiRiB1tEBPEA3bhxK0iq0VZMWpIUK1KvXmNb/HurGWbeN29KaS7ztrVVCqXJtQuPhVHCOXkARnWlUmk43APwUjegStThNT@4DFYwjDEVVrKY48YZ3GfC2OV7vYeF1nn0yVsYGd0/jMYSqGuYcTwXuWYECIcHkK0my6BDeDtEiMOhIcZLv2Dskh8Z3U2A7vo8C/6po/lXE3Pe52uCpv17mdFxssaTdJhox9t4@gQ %}
sub print-formatted ($number) {
    my $max-width = $number.base(2).Str.chars;
    my $format-string = ("%{$max-width}s" xx 4).join(" ") ~ "\n";

    for 1..$number {
        $format-string.printf($_, $_.base(8), $_.base(16), $_.base(2));
    }
}
{% endhighlight %}

            </div>
            <div class="language-commentary">

{% markdown %}
The Perl 6 solution starts of the same, in that it first calculates the max
width I need to take into account. Next, however, I generate the format string
using the `$max-width` to make the `printf` subroutine pad it for me. The `xx`
operator makes a total of 4 such strings, and puts them into a list, which I
can then `join` together with a space character, and add a `\n` at the end of
it (the `~` operator is for string concatenation).

I'm assuming something similar is possible in Python 3 as well, and I would
like to have an example so I can compare it more fairly.

In the Perl 6 solution I am also able to make use of the `base` method to
convert the numbers into the right base, something I could not find for Python
3.
{% endmarkdown %}

            </div>
        </div>
    </div>
</div>

{% markdown %}
## Wrap-up

This time I did not do all of the challenges, as the post would probably get
too long. I still did 8 of them, and might do the rest of the string challenges
in a later part anyway.

I still find Perl 6 to produce much cleaner code, which is shown best with the
first challenge. In Perl 6 (`$line.split(" ").join("-")`), I can read from left
to right to see what I'm doing: I have a `$line`, which I split, and then join.
In the Python variant (`"-".join(line.split(" "))`), it is much less clear what
the actual item I'm working on is, as it's hidden inbetween the `join` and
`split` calls.

Of course, I'm still not an expert on Python 3 code, so I'm sure that there are
many parts that could be written in a cleaner fashion. I'm still open for
feedback to improve my Python 3 skills (hence I'm publishing these posts), so
please let me know if you know better ways to solve some challenges.
{% endmarkdown %}