Proto for Boost mailing list page: [proto] no matching function

Subject: [proto] no matching function
From: Mauro Bianco (mbianco_at_[hidden])
Date: 2010-10-07 05:05:18

Hi all,
When writing a simple proto program to deal with fraction expressions 
(just an exercise to get accustomed with proto library) we run into a 
compiler error that we are not able to fix.

The aim of the exercise is to write a grammar to:
1) Remove all calls to a given function (named "Sim") in an expression: 
'Sim(Sim(Sim(a)))' is transformed into 'a'. This is a simple variation 
of the "remove-unary-plus" as found in the manual, and it works fine;
2) Remove all consecutive calls to Sim but one, so expressions like 
'Sim(Sim(Sim(a)))' will turn out be 'Sim(a)'. This does not work with 
gcc (4.3.2 and 4.3.4) and icc (11.1), but works fine with Visual Studio 
(2008 and 2010). Boost 1.44 and 1.43, Windows and Linux.

The error gcc gives is:

minimalproto.cc: In function ‘int main()’:

minimalproto.cc:73: error: no matching function for call to 
‘eval(boost::proto::exprns_::expr<boost::proto::tag::function, 
boost::proto::argsns_::list2<const 
simexpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, 
boost::proto::argsns_::term<simplifyfct>, 0l> >&, const 
frac_calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, 
boost::proto::argsns_::term<const frac&>, 0l> >&>, 2l>, frac_context&)’

....boost-1.43/include/boost/proto/eval.hpp:89: note: candidates are: 
typename boost::proto::result_of::eval<Expr, Context>::type 
boost::proto::eval(Expr&, Context&) [with Expr = 
boost::proto::exprns_::expr<boost::proto::tag::function, 
boost::proto::argsns_::list2<const 
simexpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, 
boost::proto::argsns_::term<simplifyfct>, 0l> >&, const 
frac_calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, 
boost::proto::argsns_::term<const frac&>, 0l> >&>, 2l>, Context = 
frac_context]

....boost-1.43/include/boost/proto/eval.hpp:98: note: 
typename boost::proto::result_of::eval<Expr, Context>::type 
boost::proto::eval(Expr&, const Context&) [with Expr = 
boost::proto::exprns_::expr<boost::proto::tag::function, 
boost::proto::argsns_::list2<const 
simexpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, 
boost::proto::argsns_::term<simplifyfct>, 0l> >&, const 
frac_calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, 
boost::proto::argsns_::term<const frac&>, 0l> >&>, 2l>, Context = 
frac_context]

Somebody knows what's going on?
Any insight will be highly appreciated.
Cheers,
Mauro.