Kim Kuen Tang wrote:
Dave Jenkins schrieb:
Suppose you want to move a series of additions to the right hand side. For example, transforming "var_ + 1 + 3 = 2" into "var_ = 2 - 3 - 1".
Is there a general way to iterate the Solve() transform until all the plusses are consumed? Or do you need multiple calls to Solve(), e.g. "proto::display_expr( Solve()Solve()( var_ + 1 + 3 = 2 ) );"
The grammar Solve should call himself recursively until it matches a desired expression. The stopping rule is the grammar
"proto::when<proto::assign<proto::terminal<placeholder>, _> >" .
So once the grammar "proto::when< proto::assign< proto::plus<proto::terminal<placeholder>, _>, _ > ,proto::_make_assign( proto::_left(proto::_left) , proto::_make_minus( proto::_right, proto::_right(proto::_left) ) ) >" is extended with the feature of calling Solve recursively, then multiple calls to Solve is not needed. (I am trying to implement this feature.)
That's exactly the right approach. With Proto grammars and transforms, you replace iteration with recursion.
Btw Eric, do you plan to give a session in proto in boostcon 09?
No, but I gave a session about Proto at the last 2 boostcons, and the slides are online here: http://www.boostcon.com/site-media/var/sphene/sphwiki/attachment/2009/01/26/... HTH, -- Eric Niebler BoostPro Computing http://www.boostpro.com