Re: [Boost-users] const native arrays at compile time

Subject: Re: [Boost-users] const native arrays at compile time
From: Nat Linden (nat_at_[hidden])
Date: 2012-07-12 09:04:43

On Thu, Jul 12, 2012 at 3:07 AM, Hicham Mouline <finjulhich_at_[hidden]> wrote:

> I have a number of questions, some of which are boost specific.

Hmm, haven't yet spotted the Boost questions.

> 1. const std::string cols[] = { "col1", "col2", "col3" };
> Is the const native array cols completely a compile-time construct or are
> std::string objects constructed at runtime?
> I would guess the latter?

It would surprise me greatly if any compiler would run library runtime
code at compile time in order to construct static objects.

> 2. const char const* cols[] = { "col1", "col2", "col3" };
> This on the other hand would be pure compile time?

Yes, should work even in classic C.

> 3.
> struct S1 {
> const char const* cols[]  = { "col1", "col2", "col3" };
> };
> struct S2 {
> const char const* cols[]  = { "colx", "coly", "coly" };
> };
>
> template <typename T>  /// T is either S1 or S2
> struct S {
>
>   const char const* col1s[]  = { "othercol", /// elements of T::cols  };
> };
>
> Is there a way to build col1s at compile time?

I confess I'm not sure what you're trying to accomplish here. Wouldn't
it suffice for the methods of S to directly reference T::cols ?