Re: [Boost-users] proto: BOOST_PROTO_AUTO

Subject: Re: [Boost-users] proto: BOOST_PROTO_AUTO
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2009-01-05 20:30:09

AMDG

Kim Kuen Tang wrote:
> Hi Eric,
>
> thank you for your quick response.
>
> It is interesting to see that expression like "Domain( [0,1] )"  is 
> not allowed. I think the reason is that such expression cannot be 
> transformed in a tree or the transformation is not unique.
>
> But why does the code "proto::display_expr(Domain[1,2]);" produce the 
> output:
>
> subscript(
>    terminal(domain_tag)
>    ,terminal(2)
>  )
>
> and not
>
> subscript(
>    terminal(domain_tag)
>    ,terminal(1)
>    ,terminal(2)
>  ) ?

The evaluation goes like this:

1, 2 -> 2 --- by the built in comma operator
Domain[2] -> subscript(terminal(domain_tag),terminal(2)) -- by proto's 
operator[]

In Christ,
Steven Watanabe