Patrick R. Michaud wrote:
I just want to add a reminder here that the whole reason PCT,
PAST-pm, and Tcl use morph in the first place is because Parrot
doesn't provide a usable "replace pmc with clone" opcode, and
using morph+assign is a workaround.
In other words, if a "replace pmc" opcode exists, then morph
suddenly becomes _much_ less important.
But you do want 'replace' (by whatever name) to reuse the same PMC
header as the original? i.e it's not the same as:
clone $P2, $P1
set $P0, $P2
(which would simply store a new clone in that register) but equivalent to:
morph $P0, <type of $P1>
assign $P0, $P1
(which reuses the PMC header of $P0, changes its type, and then copies
in the value from $P1).
The tricky bit is reusing a PMC header for a high-level object, whether
it's in the 'morph' opcode or some other opcode. Not impossible, though.
Ideally I'd like to have a keyed version also (choose your
own better opcode name):
replace $P0, $P1 # replace $P0 with a clone of $P1
replace $P0[key], $P1 # replace pmc at $P0[key] with a clone
# of $P1 (creating $P0[key] if needed)
Seems reasonable. Agreed it needs some naming work. It's more like
'rebless' than 'replace', but that's not right either (since we don't
have bless). It may end up as a variant of 'clone', or 'morph', or 'new'.
Allison
