Re: [boost] [proto][design]why unary_expr,binary_expr; but no nullary_expr?

From: Larry Evans (cppljevans_at_[hidden])
Date: 2008-04-27 15:56:05

On 04/27/08 06:01, Larry Evans wrote:
[snip]
> On case where this would be
Should read "one use case"
> useful is for algebraic morphisms where n-ary ops in a
> source algebra are mapped to n-ary ops in a target algebra.
> This *includes* 0-ary ops.  An op would be the equivalent
> to proto tags.  I think this could be done by another
> transform similar to the pass_through transform but
> allowing transformation of the tag. 
[snip]
The attached compiles and runs an does this algebraic
type morphism.  Maybe one thing about the attachment
is that it requires proto::expr CTOR's to be specialized
to allow the mapping. Also, I'm wondering whether
using something other than tag::terminal for 0-ary
args, i.e. args0, will lead to problems.