RFC 5, by Michael J. Mathews: Multiline comments

This is the first RFC proposed related to documentation. It asks for a common feature in most of the modern programming languages: multiline comments.

The problem of not having multi-line comments is quite obvious: if you need to comment a large chunk of code, you need to manually insert a # symbol at the beginning of every line (in Raku). This can be incredibly tedious if you do not have, for instance, a text editor to do this with a shortcut or similar. This practice is very common in large code bases. For that reason, Michael refers to C++ and Java as

popular languages that were designed from the outset as being useful for large projects, implementing both single line and multiline comments

In those languages you can type comments as follows:

// single line of code

/*
 Several lines of code
*/

But, in addition, in Java you have a special multiline comment syntax 1 for writing documentation:

/**
* Here you can write the doc!
*
*/

A lot of people proposed POD as a solution to this problem, but Michael lists some inconvenients:

  • “it’s not intuitive”: given that POD is only used by Perl, people coming from different languages will face some struggles learning an entire new syntax.

From my point of view, this not as big a problem since POD6 syntax is quite simple and it’s well documented. In addition, it is quite intuitive for newcomers: if you want a header, you use =head1, if you want italics, you use I<> and so on.

  • “it’s not documentation”: this one is still true. The main problem is that when you want to comment a big chunk of code, that’s probably not documentation, so using =begin pod ... =end pod it’s a little weird.
  • “it doesn’t encourage consistency”: another problem of POD is that you can use arbitrary terms in its syntax:
    =begin ARBITRARYTEXT 
    ... 
    =end ARBITRARYTEXT

    While this behavior gives us a lot freedom, it also complicates consistency across different projects and users.

After some discussion, Perl chose POD for implementing multiline comments. Nonetheless, Michael proposal was taken into account and Raku supports multiline comments similar to those of C++ and Java, but with a slightly different syntax:

#`[
Raku is a large-project-friendly
language too!
]
say ":D";

And as a curiosity, Raku has embedded comments, that is:

if #`( embedded comment ) True {
    say "Raku is awesome";
}

In the end, as a modern, 100-year language, Raku gives you more than one way to do it, so choose whatever fits you best!


  1. It’s not really a multiline comment because you also need to type the * symbol at the beginning of every line.

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