At 5:05 PM +0100 4/26/02, Tim Bunce wrote:
>On Fri, Apr 26, 2002 at 11:33:06AM -0400, Dan Sugalski wrote:
>> At 2:26 PM +0100 4/26/02, Nicholas Clark wrote:
>> >On Tue, Apr 23, 2002 at 01:25:15PM -0400, Dan Sugalski wrote:
>> >> At 12:36 PM -0400 4/23/02, Buddha Buck wrote:
>> >> >OK, but that limits you to the, um, 24 standard levels of
>> >> >precedence. What do you do if you don't think that that's enough
>> >>
>> >> Internally precedence is going to be stored as a floating-point
>> >> number. Dunno how it'll be exposed at the language level, but at
>> >> least there'll be more than just 20 or so levels.
>> >
>> >Why store precedence as floating point rather than integer?
>> >[Or did I miss a design document}
>>
>> Because, while you may run into problems fitting something in between
>> 1.0000001 and 1.0000002, it's not a problem to fit something between
>> 3 and 4. Floating point precedence is a problem at the edge, but
>> integer precedence makes things potentially difficult for user-added
>> operators if you want to fit things between the standard operators.
>
>Is it worth it?
I think so, yes.
>For perl at least I thought Larry has said that you'll be able to
>create new ops but only give them the same precedence as any one
>of the existing ops.
Don't recall that, though all decisions are subject to later
revision. Still, it doesn't have to be exposed either. :)
>Why not use a 16 bit int and specify that languages should use
>default precedence levels spread through the range but keeping the
>bottom 8 bits all zero. That gives 255 levels between '3' and '4'.
>Seems like enough to me!
If we're going that route, we've essentially edged over into reals of
some sort, at which point we might as well just make it a float.
>p.s. I missed the start of this thread so I'm not sure why this is
>a parrot issue rather than a language one.
It's a parrot issue in that it'll be welded into the parser part when
the parser builds up its operator precedence table.
>I also probably don't know what I'm talking about :)
I'll believe that the first time I see it actually happen... ;-P
--
Dan
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Dan Sugalski even samurai
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