Proto for Boost mailing list page: [proto] fold_tree and grammar using external_transforms and state

Subject: [proto] fold_tree and grammar using external_transforms and state
From: Joel Falcou (joel.falcou_at_[hidden])
Date: 2012-07-26 11:28:02

Here is the deal:

https://gist.github.com/3182676

THis code defines a DSL that allwo creating combo of functions using the 
following semantic:

(task(f) | task(g))(x) computes g(f(x))

(task(f) & task(g))(x) computes make_tuple<f(at<0>(x)),g(at<1>(x))>

We use external_trasnforms here because we will have other evaluation 
strategy depending on the platform. We pass the initial value to compute
as a state to the grammar and the data is the xternal transform.

The problem is that I can't get the fold_tree to work in this setup as I
guess the fold _state conflict with my own grammar _state.

Am I being dense or is it a limitation ?