Doubt Branchless code

[Richard (Rikki) Andrew Cattermole]

On 08/04/2026 12:18 PM, matheus wrote:
> On Tuesday, 7 April 2026 at 23:48:37 UTC, Richard (Rikki) Andrew 
> Cattermole wrote:
>> On 07/04/2026 7:08 AM, matheus wrote:
>>> Hello,
>>>
>>> Back in C days I used to write code with function pointer to avoid 
>>> writing branches inside loops,
>>>
>>> To avoid this:
>>>
>>> for(;;){
>>>    if(opt == 1){ func_1(); }else{func_2()};
>>> }
>>> Or maybe using switch if there were more options...
>>>
>>> So I used to do:
>>>
>>> if(opt == 1){ fp  = &func_1(); }else{ fp = &func_2()};
>>>
>>> for(;;){
>>>   fp();
>>> }
>>>
>>>
>>> I would like to know if there is a different way of doing that in D 
>>> during RT execution and dynamic change of function execution before 
>>> the loops?
>>>
>>> Thanks in advance,
>>>
>>> Matheus.
>>
>> How I typically do it:
>>
>> ```d
>> void outer() {
>>     void inner(bool a, bool b)() {
>>         for(;b;) {
>>             static if (a) {}
>>         }
>>     }
>>
>>     if (cond1 && !cond2)
>>         inner!(true, false);
>>     else if (cond2 && !cond1)
>>         inner!(false, true);
>>     else if (cond1 && cond2)
>>         inner!(true, true);
>>     else
>>         inner!(false, false);
>> }
>> ```
> 
> But this is CT, my problem was to this during RT.
> 
> Thanks anyway for responding,
> 
> Matheus.

It is optimizing RT, but we use CT to factor out the conditionals.

I've done this specifically when I would otherwise have RT if statements 
in loops.