----- Original Message ----- From: "Brent Dax" <[EMAIL PROTECTED]> To: "'TOGoS'" <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Wednesday, August 13, 2003 11:25 PM Subject: RE: set vs. assign, continued: 'add' vs. 'add!'
> TOGoS: > # syntax. As it is, the add(ints) op and the > # add(pmcs) ops do very different things (one > # has 'set' while the other has 'assign' semantics), > # but they look exactly the same. If not at > > I think that's mostly because there's no difference between set > semantics and assign semantics for ints. You can think of them as both > having assign semantics, if you like. > > # I sense the 'only people who really know > # what they're doing wil use this interface, > # anyway, so we don't have to make it nice' > # attitude in a few other places... most > # notably the Windows API. > > You don't have to lecture me on the Windows API--I use Windows, and I > have the scars to prove it. ;^) But in this case, we're doing it > because: > > a. It speeds things up. > b. It avoids a very difficult DWIM. > c. It simplifies the syntax. > > Sure, you don't need to use 'new' on an I register, while you do on a P > register--but you *never* need to use 'new' on an I, if memory serves. > So that's a consistent...uh...inconsistency between I and P registers. > > # But aside from all that, I still think > # that the set semantics for add, etc. would > # make a lot of sense in many cases, because > # the PMC that is being addded will know > # how best to return. > > The thing is, the target PMC needs a way to react to the fact that it's > being assigned to. The real semantics we want are something like: > > assign $P0, (add $P1, $P2) > > (Assuming that ops behaved that way...) > > I don't think any vtable ops actually allocate new PMCs and return > them--to my knowledge, they always operate on a target PMC. If I remember correctly, the "clone" op allocates a new PMC and stores it in the target reg. $P1 = clone $P2 # $P1 may be NULL, at least contents of $P1 are lost after this op. > I believe > that this is done for speed reasons, although I'm not sure about > that--after all, it's much cheaper to allocate target PMCs only when you > need them than to allocate them when you don't. > > --Brent Dax <[EMAIL PROTECTED]> > Perl and Parrot hacker > > "Yeah, and my underwear is flame-retardant--that doesn't mean I'm gonna > set myself on fire to prove it." > >
