Adding Unicode operators to D

[Bill Baxter]

On Mon, Oct 27, 2008 at 11:43 AM, Andrei Alexandrescu
<SeeWebsiteForEmail at erdani.org> wrote:
> Bill Baxter wrote:
>>
>> On Mon, Oct 27, 2008 at 9:04 AM, Andrei Alexandrescu
>> <SeeWebsiteForEmail at erdani.org> wrote:
>>
>>>>> What's the precedence of your user-defined in-fix operator?
>>>>>
>>>>> --bb
>>>>
>>>> Yup, I realized this myself as well. Seemed like such a great idea when
>>>> I
>>>> only thought of it for three seconds. :p
>>>
>>> An operator could always be defined to have the same precedent as an
>>> existing operator, which it has to specify.
>>
>> Walter said in a previous post a few days ago when I suggested it that
>> that would kill D's easy parsability.
>> You say no?  I'm no parser expert, so hard for me to say.
>
> It can be done, but it's kinda involved. You define a grammar in which all
> operators have the same precedence. Consequently you compile any expression
> into a list of operands and operators. That makes the language parsable
> without semanting info. Then the semantic stage transforms the list into a
> tree. Cecil does that.

I see.  So the price you pay is that you defer more decisions till
semantic stage.

I.e. "a b c d e" is allowed to parse into an amorphous list, then in
the semantic pass you decide if 'b' and 'd' are actually legal
operators or not.

--bb