Andrew Shitov

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Sorting numbers in Raku with the help of ChatGPT

In this post I will show you the solution to the Task 2 of this week’s Weekly Challenge 233. This time I was using the help of ChatGPT, which offered a very nice solution.

You are given an array of integers.
Write a script to sort the given array in increasing order based on the frequency of the values. If multiple values have the same frequency then sort them in decreasing order.

I asked ChatGPT the following: ‘Create a program. Here is the description of the task.’ To make sure the result is in the Raku programming language, I also added the following instruction in my local settings so that it knows which programming language I prefer by default.

The solution generated by ChatGPT was quite good with a small mistake.

ChatGPT: Sure, here’s a Raku program that implements the described sorting algorithm for the given task:

``````sub frequency-sort(@arr) {
my %freq;

%freq{\$_}++ for @arr;
my @sorted = @arr.sort: {
%freq{\$^b} <=> %freq{\$^a} ||
\$^b <=> \$^a
};

return @sorted;
}

my @ints = (1, 1, 2, 2, 2, 3);
my @sorted = frequency-sort(@ints);

say "Input:  @ints";
say "Output: @sorted";
``````

First, Raku would not interpolate arrays, so `say "Input: @ints"` prints the string literary: `Input: @ints`. Second, in the sorting rule, sorting by frequency must be ascending rather than descending, so we need to switch the placeholder variables `\$^b` and `\$^a`.

In the rest, ChatGPT did a good work. It computed the frequency using a loop, and I especially liked how it addressed the requirement to sort by two dimensions.

Here is the full program with the above-mentioned corrections:

``````sub frequency-sort(@arr) {
my %freq;
%freq{\$_}++ for @arr;

my @sorted = @arr.sort: {
%freq{\$^a} <=> %freq{\$^b} ||
\$^b <=> \$^a
};

return @sorted;
}

my @tests =
(1, 1, 2, 2, 2, 3),
(2, 3, 1, 3, 2),
(-1, 1, -6, 4, 5, -6, 1, 4, 1);

say frequency-sort(\$_) for @tests;
``````

This program prints the following output for the given test cases:

``````\$ raku ch-2.raku
[3 1 1 2 2 2]
[1 3 3 2 2]
[5 -1 4 4 -6 -6 1 1 1]
``````