> -----Original Message----- > From: Aleksey Gurtovoy [mailto:agurtovoy@;meta-comm.com] > Sent: Friday, November 15, 2002 7:52 AM > To: 'Boost mailing list' > Subject: RE: [boost] MPL lambda > > > Rozental, Gennadiy wrote: > > I am having hard time grasping how this %#$% lambda facility > > is working. > > I hope you mean "what it does/how to use it" as opposite to > "how it does > what it does" ;).
In fact it is second ;-) > // numbered placeholders semantics > plus<_1, int_c<5> > == bind<meta_fun2<plus>,_1,int_c<5> > > plus< int_c<5>,_1 > == bind<meta_fun2<plus>,int_c<5>,_1 > > plus< int_c<5>,_2 > == bind<meta_fun2<plus>,int_c<5>,_2 > > plus<_1,_2> == bind<meta_fun2<plus>,_1,_2> > plus<_2,_1> == bind<meta_fun2<plus>,_2,_1> > > logical_or< is_same<_1,int>, is_same<_1,long> > > = bind< meta_fun2<logical_or> > , bind< meta_fun2<is_same>,_1,int > > , bind< meta_fun2<is_same>,_1,long > > > > > is_same< _1, add_pointer<_2> > > == bind< meta_fun2<is_same> > , _1 > , bind< meta_fun1<add_pointer>, _2 > > > It would help if you start with what meta_fun[n] are, cause they are not covered in docs. Also if I understand correctly it require template template parameters. How then it works for MSVC6.5? > > // unnamed placeholder semantics > plus< _,int_c<5> > == plus<_1, int_c<5> > > plus< int_c<5>,_ > == plus< int_c<5>,_1 > > ??? == plus< int_c<5>,_2 > // can't be built using > unnamed notation > plus<_,_> == plus<_1,_2> > ??? == plus<_2,_1> > > logical_or< is_same<_,int>, is_same<_,long> > > = logical_or< is_same<_1,int>, is_same<_1,long> > > > is_same< _, add_pointer<_> > != is_same< _1, > add_pointer<_2> > // !!! > is_same< _, add_pointer<_> > > == bind< meta_fun2<is_same> > , _1 > , bind< meta_fun1<add_pointer>, _1 > // !!! > > > So the _ placeholder is substituted with appropriated numbered one based on position in expression. How did you managed to achieve this? Gennadiy. _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
