On Fri, Apr 3, 2015 at 11:13 PM, Dmitry Stogov <dmi...@zend.com> wrote:
> > > > On Fri, Apr 3, 2015 at 11:59 PM, Andrea Faulds <a...@ajf.me> wrote: > >> Hi, >> >> > On 3 Apr 2015, at 20:46, Dmitry Stogov <dmi...@zend.com> wrote: >> > >> > May be you'll also suggest something regarding bitwise shifts with >> negative offset? >> > Allowing negative offsets using opposite directions would fix >> inconsistency, but I remember, you didn't like it. >> > May be keep WARNING (Bit shift by negative number) and then perform >> shift in another direction? >> > + disable negative shifts at compile-time. >> >> I don’t think opposite-direction shifts would work well for a few >> reasons. I don’t believe this is normal behaviour in other languages, for >> one. Another issue is that << and >> are not actually opposites, they have >> different behaviour with respect to signs, so there’d be ambiguity as to >> what $x << -$y means (is it the same as $x >> $y, or does it deal >> differently with signs?). Negative shifts being used are usually the result >> of mistakes, as well, so you want to inform the user. >> >> The main problem, though, is that we previously did something different >> if the shift is negative. Having it now produce a warning, means you’ll see >> error messages when you run existing code. But shifting in the opposite >> direction might change the behaviour of existing code silently >> >> I think the most sensible solution would be to make negative shifts >> produce an exception, since they’re really an error, an unsupported >> operation. I made them be a warning + return FALSE just because it matched >> division. But that’s not ideal and I’d be fine if it was replaced. >> > > OK. Exception is fine. > > So the summary: > > 1) division by zero produces a warning and +/-INF IS_DOUBLE. Compile-time > evaluation is disabled. > > 2) Negative shift produces Exception.Compile-time evaluation is disabled. > > 3) Modulo by zero produces Exception.Compile-time evaluation is disabled. > > Everything right? > Don't think we need to disable compile-time evaluation for 2) and 3). It'll just end up being a compile error in that case. I think if you have 1 % 0 occurring in your code literally, it's better to have the compile fail rather than getting (or not getting) a runtime exception. Nikita
