Advent Calendar - December 19, 2022

Advent Calendar 2022

| Day 18 | Day 19 | Day 20 |

The gift is presented by Stephen G. Lynn. Today he is talking about his solution to “The Weekly Challenge - 186”. This is re-produced for Advent Calendar 2022 from the original post by him.

Challenge 1 (Zip List)

Challenge 1 requires "zipping" two lists a and b say, by creating a combined list in which the elements are: (a[0] b[0] a[1] b[1] a[2] b[2] ...). The lists are of equal length.

There are ready-made functions to do this in all three languages I submit. In Perl 5, List::MoreUtils has a zip function that does exactly this. Raku has the Z operator, so it is as simple as @a Z @b. Julia has a zip function named zip, though the output is not quite what is requested. It returns an array of tuples: [(a[0] b[0]), (a[1] b[1]), ...].

I wrote my own function for the task, using straightforward logic. I just push the elements of the two arrays into a new array in the prescribed order. The key snippet:

Perl 5

push @c, ($$ra_a[$_], $$ra_b[$_]) for (0 .. @$ra_a-1);

Raku

@c.append(@a[$_], @b[$_]) for (0 .. @a-1);

Julia

for i in 1:length(b)
    append!(c, a[i], b[i])
end

Here is my Perl 5 script.

Here is my Raku script.

Here is my Julia script.

Challenge 2 (Unicode makeover)

This challenge requires replacing a string of accented alphabets say 'âÊíÒÙ' with the unaccented equivalent say 'aEiOU'.

I was under the impression that accented alphabets were formed by two-character sequences where the second character was in the range U+0300 to U+036F. If so, one could use a regex to strip the input string of characters in this range and we are through.

This is not how it works though, as I found out when I tried and failed with the regex, and peeked at the codes for the accented characters in the test string.

I finally wound up using a ready-made UNIX utility iconv. I embed a call to iconv in my Perl 5 and Raku subroutines using the backtick quoting in Perl 5, and the equivalent qqx quotes in Raku.

The key snippet:

Perl 5

return `echo $string | iconv -f utf-8 -t ascii//translit`;

Raku

return qqx{echo $string | iconv -f utf-8 -t ascii//translit};

I tried to do the same in Julia, but could not get the piping to work correctly. Julia however has an easy way to do this via the Unicode.normalize function.

The key snippet from my Julia script:

return Unicode.normalize(str, stripmark=true)

Raku also has an instant built-in way to do this via the samemark routine.