petdance/scratch — Issue #949: Unreasonably painful to add a method to all *Array PMCs
Author: petdance
Created: 2011-11-14 06:14:07+00:00
State: open
Labels: core, Pri-normal, rfc, Sev-medium

Adding a method that works for all *Array PMCs (in either PIR or NQP) should be really easy, but it isn't. If all *Array PMCs had a common ancestor (Array, say), you could do this:
```
module Array {
method reverse () {
my @reversed;
for self { @reversed.unshift($_); }
@reversed;
}
}
```

Unfortunately, there is no such common ancestor. Likewise, they
share no common role, so that's not an in either.

One could copy and paste the above block for each *Array module, but that's just nuts. Talk about a DRY violation.

It's possible one might create one method code object, then iterate over all the known *Array types and use add_method to add that code to them as a method, but this will fail if the list of *Array types changes, which it reasonably might. Plus it's just ugly for what should be a simple task.

Originally http://trac.parrot.org/parrot/ticket/1416 by @japhb