Re: Time to kill T() as (sometimes) working T.init alias ?

[Maxim Fomin]

On Thursday, 29 November 2012 at 10:41:46 UTC, Mehrdad wrote:
I'm just not understanding the whole "the default construction 
of a struct should be a compile time creature, not a runtime 
one".



Don't you have to initialize the struct with zero's either way?

So either way, you're going to have to initialize it... so no 
perf increase in any way. Why prevent the user from 
default-initializing it the way he wants to?

Every type has a CT-known default initializer, even classes have 
(null). If structures had a runtime one, this would break code 
(especially templates and CTFE) which relies on knowing something 
about constant default instance of a type at CT.

extern bool foo();

struct S
{
  int i;
  this() {
    i = foo() ? 1 : -1;
  }
}
---------
S s;
dosmth(s);
---------
//somewhere in Phobos

void dosmth(T) (T obj)
{
  T val; // is i 0, -1 or 1 ?
}