Leopold Toetsch wrote: > I currently can't imagine any useful RL example for the current > implementation of set_p_p as $1=$2, _if_ the involved PMC types are > different.
You need to differentiate between the PMC itself, and a Parrot register that holds the address of a PMC. In the instruction "set Px, Py" the only PMC involved is the one pointed to by register Py; if Px happens to point to a PMC then that linkage will be broken, with no effect on the PMC (previously) pointed to by Px; the register Px will then point to the same PMC as Py does. In the code snippet you originally posted, there seemed to be no need for this; however, calling subroutines, for example, will require that the addresses of the parameters be placed in specific registers, and so the set operation may well be used frequently in those circumstances. The instruction that performed the actual assignment to the PMC was the "set Px, 2" instruction; this (which may be replaced by "assign") calls the set_integer_native vtable method. Since the PMC type is PerlUndef at that point, the current automatic morphing kicks in, and the PMC actually gets turned into a PerlInt - in future, the perl compiler will have to create a PMC with the correct type initially, and this morphing will be removed for typed variables. -- Peter Gibbs EmKel Systems
