Re: [Boost-users] [Proto] callable_context
Dear Erik,
lit(1) >> &f >> &g >> &h
So, what about this new one in Proto?
Yes, that should be doable.
OK, that's good news. Here is my attempt to get it done (assuming that we only pipe integers into series of functions): struct FuncStreamCtx: callable_context<const FuncStreamCtx> { FuncStreamCtx() {} typedef int result_type; int operator () (tag::terminal, int i) const {return i;} template<typename L, typename R> int operator () (tag::shift_right, const L& l, const R& r) const { int arg = eval<L, const FuncStreamCtx>(l, *this);//*** int (*f) (int) = value(r); return f(arg); } }; (I know you told me that contexts make life hard. But, I'm not still comfortable with transforms...) Now, when I try to compile this code (GCC 4.5.1, MinGW32, WinXP, SP3), I get the error in the P.S. for trying it with: cout << eval(lit(51) >> &plus2, ctx);
From what I understand, from line ***, GCC mistakenly thinks that I'm trying to instantiate eval<> and fails to find an appropriate ctor -- it only nags about finding the default and the copy one. Strangely enough, when I remove the template arguments from the same line, I get:
error: missing template arguments before '(' token Any ideas? TIA, --Hossein P.S. -------------- Build: Debug in ProtoGame3 --------------- Compiling: main.cpp D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp: In member function 'int FuncStreamCtx::operator()(boost::proto::tag::shift_right, const L&, const R&) const [with L = boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain>, R = boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<int (* const&)(int)>, 0l>]': D:\Sources\Boost\boost_1_42_0/boost/proto/context/callable.hpp:313:21: instantiated from 'boost::proto::context::callable_eval<Expr, Context, 2l>::result_type boost::proto::context::callable_eval<Expr, Context, 2l>::operator()(Expr&, Context&) const [with Expr = const boost::proto::exprns_::expr<boost::proto::tag::shift_right, boost::proto::argsns_::list2<const boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain>&, boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<int (* const&)(int)>, 0l> >, 2l>, Context = const FuncStreamCtx, boost::proto::context::callable_eval<Expr, Context, 2l>::result_type = int]' D:\Sources\Boost\boost_1_42_0/boost/proto/eval.hpp:100:62: instantiated from 'typename boost::proto::result_of::eval<Expr, Context>::type boost::proto::eval(Expr&, const Context&) [with Expr = const boost::proto::exprns_::expr<boost::proto::tag::shift_right, boost::proto::argsns_::list2<const boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain>&, boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<int (* const&)(int)>, 0l> >, 2l>, Context = FuncStreamCtx, typename boost::proto::result_of::eval<Expr, Context>::type = int]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:38:37: instantiated from here D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:23:50: error: no matching function for call to 'boost::proto::context::callable_context<const FuncStreamCtx>::eval<boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain> >::eval(const boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain>&, const FuncStreamCtx&)' D:\Sources\Boost\boost_1_42_0/boost/proto/context/callable.hpp:223:17: note: candidates are: boost::proto::context::callable_context<const FuncStreamCtx>::eval<boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain> >::eval() D:\Sources\Boost\boost_1_42_0/boost/proto/context/callable.hpp:223:17: note: boost::proto::context::callable_context<const FuncStreamCtx>::eval<boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain> >::eval(const boost::proto::context::callable_context<const FuncStreamCtx>::eval<boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain> >&) Process terminated with status 1 (0 minutes, 19 seconds) 3 errors, 0 warnings
Just wanted to say that I solved the problem by delegating the task of evaluation to a dummy call forwarder: struct FuncStreamCtx: callable_context<const FuncStreamCtx, null_context> { FuncStreamCtx() {} typedef double result_type; double operator () (tag::terminal, double i) const {return i;} template<typename L, typename R> double operator () (tag::shift_right, const L& l, const R& r) const { double arg = evaluate_helper(l, *this); double (*f) (double) = value(r); return f(arg); } }; template<typename Expr> double evaluate_helper(const Expr& e, const FuncStreamCtx& ctx) { return boost::proto::eval(e, ctx); } template<typename Expr> double evaluate(const Expr& e) { const FuncStreamCtx ctx; return evaluate_helper(e, ctx); } --- On Wed, 5/1/11, Hossein Haeri <powerprogman@yahoo.com> wrote:
From: Hossein Haeri <powerprogman@yahoo.com> Subject: Re: [Boost-users] [Proto] callable_context To: boost-users@lists.boost.org Date: Wednesday, 5 January, 2011, 15:31 Dear Erik,
lit(1) >> &f >> &g >> &h
So, what about this new one in Proto?
Yes, that should be doable.
OK, that's good news. Here is my attempt to get it done (assuming that we only pipe integers into series of functions):
struct FuncStreamCtx: callable_context<const FuncStreamCtx> { FuncStreamCtx() {}
typedef int result_type;
int operator () (tag::terminal, int i) const {return i;}
template<typename L, typename R> int operator () (tag::shift_right, const L& l, const R& r) const { int arg = eval<L, const FuncStreamCtx>(l, *this);//*** int (*f) (int) = value(r); return f(arg); } };
(I know you told me that contexts make life hard. But, I'm not still comfortable with transforms...)
Now, when I try to compile this code (GCC 4.5.1, MinGW32, WinXP, SP3), I get the error in the P.S. for trying it with:
cout << eval(lit(51) >> &plus2, ctx);
From what I understand, from line ***, GCC mistakenly thinks that I'm trying to instantiate eval<> and fails to find an appropriate ctor -- it only nags about finding the default and the copy one. Strangely enough, when I remove the template arguments from the same line, I get:
error: missing template arguments before '(' token
Any ideas?
TIA, --Hossein
P.S.
-------------- Build: Debug in ProtoGame3 ---------------
Compiling: main.cpp D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp: In member function 'int FuncStreamCtx::operator()(boost::proto::tag::shift_right, const L&, const R&) const [with L = boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain>, R = boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<int (* const&)(int)>, 0l>]': D:\Sources\Boost\boost_1_42_0/boost/proto/context/callable.hpp:313:21: instantiated from 'boost::proto::context::callable_eval<Expr, Context, 2l>::result_type boost::proto::context::callable_eval<Expr, Context, 2l>::operator()(Expr&, Context&) const [with Expr = const boost::proto::exprns_::expr<boost::proto::tag::shift_right, boost::proto::argsns_::list2<const boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain>&, boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<int (* const&)(int)>, 0l> >, 2l>, Context = const FuncStreamCtx, boost::proto::context::callable_eval<Expr, Context, 2l>::result_type = int]' D:\Sources\Boost\boost_1_42_0/boost/proto/eval.hpp:100:62: instantiated from 'typename boost::proto::result_of::eval<Expr, Context>::type boost::proto::eval(Expr&, const Context&) [with Expr = const boost::proto::exprns_::expr<boost::proto::tag::shift_right, boost::proto::argsns_::list2<const boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain>&, boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<int (* const&)(int)>, 0l> >, 2l>, Context = FuncStreamCtx, typename boost::proto::result_of::eval<Expr, Context>::type = int]' D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:38:37: instantiated from here D:\My Documents\My Programmes\Tutorial\Proto\ProtoGame3\main.cpp:23:50: error: no matching function for call to 'boost::proto::context::callable_context<const FuncStreamCtx>::eval<boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain>
::eval(const boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain>&, const FuncStreamCtx&)' D:\Sources\Boost\boost_1_42_0/boost/proto/context/callable.hpp:223:17: note: candidates are: boost::proto::context::callable_context<const FuncStreamCtx>::eval<boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain> ::eval() D:\Sources\Boost\boost_1_42_0/boost/proto/context/callable.hpp:223:17: note: boost::proto::context::callable_context<const FuncStreamCtx>::eval<boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain> ::eval(const boost::proto::context::callable_context<const FuncStreamCtx>::eval<boost::proto::utility::literal<const int&, boost::proto::domainns_::default_domain> &) Process terminated with status 1 (0 minutes, 19 seconds) 3 errors, 0 warnings
_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
participants (1)
-
Hossein Haeri