how to refer to a sub exported by a module when using require?

Question

Background: There are a number of modules in the local lib eg Eg-1.rakumod Eg-2.rakumod Eg-3.rakumod, each Eg-\d is referenced in META6.json file, and each module has the code

sub SITE is export { ... }

Clarification: SITE is written in each example so the SITE.routes generates a CRO route set.

When another program eg., show-example.raku, is written with

use Eg-1;
my $routes = SITE.routes;

show-example.raku compiles and runs. SITE is in the namespace and yields a structure to be stored in $routes.

However, if we have in show-example2.raku

my @egs = <Eg-1 Eg-2 Eg-3>;
my $option = 1; # pointing to Eg-2
require ::(@egs[1]);
my $routes = SITE.routes

running raku -I. show-example2.raku fails to compile. Naturally because at compile time SITE is not known to be the name of a sub, although it will be known at runtime.

The question is how to refer to a sub that is known at runtime?

However, this does not seem to work:
my $routes = &::(@egs[1])::SITE.routes

error: No such symbol Eg-2::&SITE

require ::(@egs[1]) <&SITE>;? also your last attempt would work if &SITE is declared our (it's my by default) — Mustafa Aydın
– Mustafa Aydın, Commented Aug 2 at 12:34
Raku's standard default export mechanisms (which is export is a part of) store any exported symbols (subs or any other) in a Stash (Symbol table hash) named DEFAULT (or other :tag if is export(:tag) is used) plus another called ALL. Symbols corresponding to these Stashes are in turn stored in another Stash named EXPORT. And a symbol corresponding to that is stored in the Stash corresponding to the package whose symbols are being exported (in your code, the one ::(@egs[1]) refers to). Your presumption that it was otherwise is wrong but understandable. — raiph
– raiph, Commented Aug 4 at 12:19
So, for a solution along the lines you were thinking about when you wrote &::(@egs[1])::SITE you would need to instead write &::(@egs[1])::EXPORT::DEFAULT::SITE. I'm currently planning to finish and post an answer that expands on the many topics I think worth covering. — raiph
– raiph, Commented Aug 4 at 15:11

Richard Hainsworth · Accepted Answer · 2025-08-02 18:21:14Z

0

One suggestion that works is to avoid require and use use in a restricted sense.

my @egs = <Eg-1 Eg-2 Eg-3>;
my $option = 1; # pointing to Eg-2
my $routes = "use @egs[$option]; SITE.routes".EVAL;

answered Aug 2 at 18:21

Richard Hainsworth

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raiph Aug 4 at 12:25

I'd say that is using the mother (or should I say MONKEY?) of all hacks! 🤣 I am preparing an answer that will provide the clean solution that the relevant mechanisms provide and that Rakoons are supposed to use, and a detailed explanation of those mechanisms, and how I would characterize the initial mistakes you made, and why I think others didn't figure out the simple answer.

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