Why is D unpopular?

[Walter Bright]

On 4/30/2022 10:17 PM, Ola Fosheim Grøstad wrote:
> My point was that it did propose CTFE,

Nope. It proposed more syntax for something else. I wasn't sure what, as the 
examples and text apparently needed the verbal part of the presentation to make 
sense. I don't know what "metacode injection" is or what it has to do with CTFE.


> and the presentation states that they had 
> a prototype compiler extension for it, back in 2003.

It says "partially implemented", not a prototype. It also seems to have nothing 
in common with Bjarne's proposal 4 years later.


> D also makes some unsound assumptions by assuming that the hardware you compile 
> on is giving the same answer as the hardware you execute on That can give
> surprising results, bugs that are nigh impossible to pinpoint, because you don't 
> get them on your development machine. Are you really sure you want that?

Are you sure D's CTFE does that? (CTFE doesn't allow unsafe code, for example.) 
Are you sure C++'s does not? D is much more portable between systems than C++ 
is, in particular things like the sizes of types.


> Thankfully consteval gives you full control over what happens when.

That's the C++ rationale for consteval. But D allows 100% control over whether 
CTFE is run or not. consteval is completely unnecessary. It's simple - CTFE is 
run if otherwise the compiler would give an error message that it cannot resolve 
an expression at compile time. For example,

void test()
{
     enum e = foo(); // runs foo() at compile time
     auto f = foo(); // runs foo() at run time
}

------

CTFE is conceptually a no-brainer. Run a function at compile time. That's it. 
Neither Daveed's nor Bjarne's proposals do that. Zero new syntax is necessary.