Ok, I hereby volunteer to update the documentation to clearly explain shifting (with examples).
-Jason On Wed, 2002-10-30 at 14:05, James Cox wrote: > We're going to walk into a confusion where people will expect <<< to work > too, and get bitten. We have to be really careful that we explain it > properly. > > -- james > > > > > I think you guys have convinced me that having >>> only isn't too bad > > (Jason will kill me now). > > Does anyone here on php-dev have any additional thoughts? > > I just want to point out that what convinced me wasn't the "anyone who > > knows twos complement would know that blah blah blah" argument. Don't > > forget that most of our PHP users aren't always that knowledgeable and we > > need to understand and respect that. Anyway, I just wanted to say that > > because I often get the feeling that people on php-dev forget that it's > > usually the more computer science oriented people on this list > > which isn't > > necessarily the average PHP user. > > > > Andi > > > > At 11:39 AM 10/29/2002 -0600, Jason T. Greene wrote: > > >On Thu, 2002-10-24 at 09:51, David M. Lloyd wrote: > > > > On Thu, 24 Oct 2002, Andi Gutmans wrote: > > > > > > > > > At 02:49 PM 10/23/2002 -0500, David M. Lloyd wrote: > > > > > > > > > > >The reality of twos-complement, bitwise arithmatic is that > > there are > > > > > >three basic shift operations: shift left, bitwise shift right, and > > > > > >arithmetic shift right. This simple fact is one of the > > basic ideas of > > > > > >dealing with twos-complement integers. > > > > > > > > > > I know that but I still wanted the opposite to be available to keep > > > > > things symmetrical. I'm not sure but I think CPU's do support both > > > > > logical and arithmetic shifts and just do the same with > > both (I might be > > > > > wrong though). > > > > > > > > Generally no, it's a waste of opcode space for modern CISC processors. > > > > RISC processors often have integrated barrel-shifters, so > > they don't need > > > > shift instructions at all. > > > > > > > > Intel carries over "arithmetic" shift right instructions from older > > > > architetures for backwards-compatibility with x86, but their RISC > > > > implementation (Itanium) does not contain support for the operation. > > > > > > > > One RISC example is ARM. They give you four shift options: > > Logical left, > > > > logical right, arithmetic right, and rotate right. Making > > the operation > > > > symmetrical is a waste of precious bit combinations, and > > would have meant > > > > either losing another shift operation or else adding another > > bit to the > > > > shift operation specifier, which means that another bit would > > have to be > > > > sacrificed elsewhere. > > > > > > > > Another example is SPARC, which implements shifting with discrete > > > > instructions, only implents one left shift operator. PowerPC does not > > > > implement it either. > > > > > >Alpha has 3 instructions as well (log left, log right, arith right) > > > > > > > > >Given this fact, there is no reason to have a bogus fourth > > operator > > > in the > > > > > >name of symmetry. Mathematical operaters are simply not always > > > > > >symmetrical. There is no such thing as 'arithmetic shift left' or > > > > > >'logical shift left' in terms of twos-complement integers, > > so why invent > > > > > >it? > > > > > > > > > > I agree that they don't *have* to be symmetrical but I think it's > > > > > better. > > > > > > > > Better why? Anyone who understands twos-complement will > > understand (and > > > > expect) the ability to do those three operations, and will not be > > > > surprised by the lack of two left shifts. I argue that they > > *should NOT* > > > > be symmetrical because it is wrong. > > > > > >I have to say I agree, introducing a bogus operator could actually cause > > >confusion. Java, which has been used several times in past arguments of > > >"why we should not do XYZ", has not had a problem with having only the > > >operators that actually exist. > > > > > > > > >Second of all, my understanding of the here-doc operator > > is that it acts > > > > > >as a unary operation. I don't see the conflict with the binary > > > > > >application of <<<, given the example of unary and binary > > -, if it is > > > > > >absolutely neccessary to fulfill the (somewhat psychotic) need for > > > > > >symmetry where it is not realy needed, or even strictly correct. > > > > > > > > > > psychotic? Can we please have discussions on a professional and not > > > > > personal level? > > > > > > > > It is true though, unless you can give me a sound > > mathematical reason that > > > > the ops should exist... and saying "it looks right" or "it is > > easier" is > > > > not a valid reason, becuase to those with even basic > > twos-complement math > > > > background, it looks wrong and is not easier. > > > > > > > > > As far as I remember it does clash with here-docs. I'm pretty sure I > > > > > thought of an example a while back. I can try and think of > > one again. In > > > > > any case, I wouldn't want an overloaded operator. We try > > and keep away > > > > > of that kind of stuff with PHP. > > >Clashing can occur with Constant values, and functions with a \n in > > >front of the (). > > > > > > > Very well... then let's not put in the nonsense operator, and > > just have > > > > three shift operations: <<, >>, and >>>. > > > > > >I agree > > > > > > > - D > > > > > > > > <[EMAIL PROTECTED]> > > > > > > > > > > > > -- > > > > PHP Development Mailing List <http://www.php.net/> > > > > To unsubscribe, visit: http://www.php.net/unsub.php > > > > > > >-Jason > > > > > >-- > > >Jason T. Greene <[EMAIL PROTECTED]> > > > <[EMAIL PROTECTED]> > > > > > > > > > > > > > > >-- > > >PHP Development Mailing List <http://www.php.net/> > > >To unsubscribe, visit: http://www.php.net/unsub.php > > > > > > -- > > PHP Development Mailing List <http://www.php.net/> > > To unsubscribe, visit: http://www.php.net/unsub.php > > > > > -- PHP Development Mailing List <http://www.php.net/> To unsubscribe, visit: http://www.php.net/unsub.php
