SOURCE Cromwell Enage <sponage@[...].com>  writes:

>  I remember a thread that ran for a while on this
>  topic, and I need to make sure I've wrapped my head
>  around it correctly.  

I think you're referring to Vesa Karvonen's Lazy MPL (not sure if
that's what he called it).

>  Here are my takes on laziness:
> 
>  <take id="point-1">
>  A metafunction returns lazily if it can be used
>  interchangeably with its return type.  

I don't think that's the right way to think about it; Vesa's laziness
is not about how things are returned, but about the treatment of
arguments.  A valid lazy metafunction argument is one that has a
nested ::type.  In other words, all lazy metadata are MPL nullary
metafunctions.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com

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