Re: MAIN(*magic)

> On 15 Mar 2024, at 03:57, Mark Devine <[email protected]> wrote:
> 
> Rakoons,
>  I keep running into a space with Raku where it would be nice to have some magic to reduce boilerplate.  I often make roles & classes with interface options that flow from a consuming script’s MAIN arguments, then the first bit of code at the top the MAIN block, then into instantiation.  If a person makes nice utility libraries with lots of options for the user & employs them a lot, the time consumed typing out the boilerplate adds up & bloats the code.  Is there any way to shorten this pattern?  I was thinking about a ‘switchable’ trait for attributes (with the naivety of a schoolboy).
>  my class Output {
>     has $.csv      is switchable;
>     has $.html     is switchable;
>       .
>       .
>       .
>     has $.xml     is switchable;
> }
>  my class Timer {
>     has $.count    is switchable;
>     has $.expire   is switchable;
>     has $.interval is switchable;
> }
>  sub MAIN (
>     Output.switchables,     #= switchables from Class 'Output'
>     Timer.switchables,      #= switchables from Class 'Timer'
> ) {
>     my Timer $t    .= new: :$expire, :$interval, :$count;   # variables magically appear in scope
>     my Output $o   .= new: :$csv, :$html, … , :$xml;        # variables magically appear in scope
> }
>  I estimate 10-50 lines of boilerplate could be removed from most of my Raku scripts with something like that.  Unfortunately, I don’t possess any dark magic for such things or I’d put forward an attempt.

An interesting idea!

Unfortunately I don't see this happening in the legacy grammar.  And it may still be pretty hard to do in RakuAST.

If you'd want to have a solution now, I'd look at *generating* the boilerplate code where appropriate.  This approach is used in the core in several locations, most notably recently in the localization modules.


Liz