c++ - Style of programming templates -

if having option, 1 choose?

template<class checkeverynode<true>> struct x;  or   template<bool checkeverynode> struct x; 

that isn't obvious designers perspective, on 1 side have readability in actual code:

//taking first approach //somewhere in code x<checkeverynode<false>> x; 

on second side there more type , prefer:

//taking second approach //somewhere in code x<false> x;//but here don't see false means.   

so, looking forward opinions/suggestions

often dabbling in metaprogramming, can recommend "verbose" approach, don't quite first approach propose.

ideally, when using policies, don't pass flag, pass policy object, allow user customize @ will, rather relying on own predefined values.

for example:

struct nodecheckertag {};  struct checkeverynode {   typedef nodecheckertag policytag;   void check(list const& list); };  struct checkfirstnode {   typedef nodecheckertag policytag;   void check(list const& list); };  template <typename rand> struct checksomenodes {   typedef nodecheckertag policytag;   checksomenodes(rand rand): _rand(rand) {}   void check(list const& list);   rand _rand; }; 

your class should allow user choose policy elect:

template <typename nodechecker> class x: nodechecker // allow stateful implementation let ebo kick in { }; 

the policytag presence of several policies:

template <typename nodechecker, typename nodeallocator, typename nodenotifier> class x; 

you should provide sensible defaults, there case of i want customize last!, switching variadic template, can that:

template <typename tag, typename default, typename... policies> struct policyselector {   typedef /**/ type; };  template <typename... policies> class x: policies... {   typedef typename policyselector<nodecheckertag, checknonode,     policies...>::type nodecheckerpolicy;   typedef typename policyselector<nodeallocatortag, stdallocator,     policies...>::type nodeallocatorpolicy;   ... }; 

note inheriting policies, selection might unnecessary if care invoking functions. it's necessary if need inner typedefs hidden in policies should explicitly typedef'd in derived class (x here).