Re: [boost] [proto]howto generate extended tree top down instead of bottom up?

From: Larry Evans (cppljevans_at_[hidden])
Date: 2007-07-08 08:54:24

On 07/07/2007 11:49 AM, Eric Niebler wrote:
[snip]
>      template<typename Expr>
>      struct wrap
>      {
>          explicit wrap(Expr const &expr)
>          {}
>      };
> 
Thanks very much Eric; however, I found that with the following:

      template<typename Expr>
      struct wrap
      #define INHERIT_EXPR
      #ifdef INHERIT_EXPR
      : Expr
      #endif
      {
          explicit wrap(Expr const &expr)
          {
              std::cout<<"Wrap::CTOR\n";
          }
      };

the wrap CTOR is not called when:

          WrapItUp::call( _1 + _2, i, i );

is executed.  OTOH, if INHERIT_EXPR is undefined,
then wrap CTOR *is* called.  There must be some typedef needed
by wrap in order for WrapItUp::call to actually call
the wrap CTOR.  I'll start looking for it, but I'd
appreciate any clues.

TIA.

-Larry