opConcatAll?

[Steven Schveighoffer]

On 7/3/20 11:39 AM, Andrei Alexandrescu wrote:
> On 7/3/20 3:17 AM, Petar Kirov [ZombineDev] wrote:
>> On Thursday, 2 July 2020 at 20:26:15 UTC, Steven Schveighoffer wrote:
>>> On 7/2/20 3:28 PM, Nick Treleaven wrote:
>>>> On Thursday, 2 July 2020 at 15:47:39 UTC, Steven Schveighoffer wrote:
>>>>> a ~ b ~ c ~ d
>>>>>
>>>>> will translate to
>>>>>
>>>>> a.opConcatAll(b, c, d)
>>>>
>>>> Sounds good, although I think multiple other operations beside 
>>>> concatenation could benefit from being intercepted:
>>>>
>>>> opNary(string op, T...)(T args)
>>>>
>>>> E.g. perhaps BigInt can avoid one or more reallocations for >2 args. 
>>>> The compiler would try opNary first in that case, and fallback to 
>>>> successive calls to opBinary as now.
>>>>
>>>> In fact, maybe some types could benefit from intercepting different 
>>>> operations at once:
>>>>
>>>> opNary(string[] ops, T...)(T args)
>>>
>>> That would be awesome, and cover my case!
>>
>> We kind of have this already, but a bit closer to what jmh was 
>> describing earlier.
>> Though it's just an implementation detail inside druntime for 
>> implementing array ops:
>>
>> https://github.com/dlang/druntime/blob/v2.092.1/src/core/internal/array/operations.d#L15-L36 
>>
>>
>> I think that it would be pretty cool if this technique could be 
>> applied to user-defined types (e.g. allow library authors to provide 
>> their own `arrayOp` implementation of their types).
> 
> How are parens handled?

There are possibilities. The array vector operations seem to be passed 
in RPN, negating the need for parentheses handling (maybe the compiler 
translates the expression for you?)

Another possibility is just to stop at parentheses boundaries. e.g.:

(a + b + c) * d => a.opNary!(["+", "+"])(b, c).opBinary!"*"(d);

Which isn't as powerful, but still helpful in many cases.

-Steve