I'm a missionary in Japan. The name of my mission agency is WEC International. That's supposedly Worldwide Evangelisation for Christ, but I think I have a better idea about what it stands for...
2006-08-21
Perl parameter passing
Jesse set me a challenge: make Perl 6-style parameter handling work in Perl 5. Without source filters. This is hard. But not, as was earlier claimed, impossible. When people say things are impossible with Perl, it just makes me want to go on and do them.
I've done this proof of concept:
package foo;
use Method;
sub new { bless {} }
sub bar :method { print $self; }
foo->new->bar();
The way it works is: all marked subroutines are scanned, and a pad
(my) variable $self is allocated if there
isn't one already. Then all references to $self the
global - as in the method above - are converted into references to
the lexical variable. Then - and this is the horrific bit - a bunch
of Perl ops are injected into the code stream at the beginning of
the method, like so:
OP* padop = newOP(OP_PADSV, 0);
OP* assignop =
newASSIGNOP(OPf_STACKED,
padop,
0,
newUNOP(OP_SHIFT, 0,
newAVREF(newGVOP(OP_GV, 0, PL_defgv))
)
);
OP* startop = Perl_linklist(aTHX_ assignop);
padop->op_targ = offset;
assignop->op_next = op->op_next;
op->op_next = startop;
From there to full-blown Perl 6 parameter parsing is a simple matter of programming...
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lathos: seriously hating on RapidSwitch at the moment. They're useless.
