c++ - Handle partial type with Boost Hana -


what call partial type here that:

template < template <typename ...> typename skeleton,            template <typename ...> typename wrappertype,            typename ... pölicies > struct metastorage {    template < typename ... ts >   struct with_type {      using type = skeleton<wrappertype<ts...>, policies...>;   }; };  using partialtype = metastorage<sk, wt, p1, p2, p3>; using finaltype = partialtype::with_type<t1, t2>;

i don't think fits hana philosophy , it's not readable if want split type more this.

so efficient way of doing boost hana?

edit :

by mean, way allow user create final type in several steps. can use partial type generate every final type. usual syntax , hana::type.

with boost.hana can lift types values hana::type , same templates using hana::template_. can following:

#include <boost/hana.hpp>  namespace hana = boost::hana;   template <typename ...x> struct skeleton_t { }; constexpr auto skeleton = hana::template_<skeleton_t>; template <typename ...x> struct wrapper_t { }; constexpr auto wrapper = hana::template_<wrapper_t>; template <int i> struct policy_t { }; template <int i> constexpr auto policy = hana::type_c<policy_t<i>>; template <int i> struct foo_t { }; template <int i> constexpr auto foo = hana::type_c<foo_t<i>>;  int main() {   auto meta_storage = [](auto s, auto w, auto ...policies) {     return [=](auto ...ts) {       return s(w(ts...), policies...);     };   };    auto partial = meta_storage(skeleton, wrapper, policy<1>, policy<2>);    auto final_ = partial(foo<1>, foo<2>);    skeleton_t<wrapper_t<foo_t<1>, foo_t<2>>, policy_t<1>, policy_t<2>> check     = typename decltype(final_)::type{}; }

personally prefer not bother hana::template_ in cases can use function. use macro create tag type along corresponding hana::type value reduce of setup see above main function.


Comments

Post a Comment

Popular posts from this blog

commonjs - How to write a typescript definition file for a node module that exports a function? -

consider, toml node module can use: // toml.d.ts declare module toml { export function parse(value:string):any; } declare module "toml" { export = toml; } then: /// <reference path="../../../../../defs/toml/toml.d.ts"/> import toml = require('toml'); toml.parse(...); however, node module export single function, such 'glob' ( https://github.com/isaacs/node-glob ). the node usage of module be: var glob = require("glob") glob("*.js", {}, callback(err, files) { ... }); you'd naively expect this: // glob.d.ts declare function globs(paths:string, options:any, callback:{(err:any, files:string[]):void; ...but because typescripts 'import' semantics bit strange, seems can use 'import .. = require()' statement alias modules . trying call: /// <reference path="../../../../../defs/glob/glob.d.ts"/> import blog = require('glob'); results in: error ts2072: mod...
Read more

openid - Okta: Failed to get authorization code through API call -

i'm integrating okta own idp server using okta's api. i'm implementing authorization code flow following steps below: in own server, use /api/v1/authn endpoint sessiontoken. use sessiontoken obtain authorization calling endpoint: /oauth2/v1/authorize?client_id=" + clientid + "&sessiontoken=" + sessiontoken + "&response_type=code&response_mode=query&scope=openid&redirect_uri=" + redirecturl + "&state=evanyang&nonce=" it's supposed return response status code 302 , location header containing redirect url code value. however, keep getting response status code 200 , without location header, html body saying "you using unsupported browser." , "javascript disabled on browser." according api documentation: http://developer.okta.com/docs/api/resources/oidc.html#authentication-request , sessiontoken parameter sufficient this: an okta one-time sessiontoken. allows api-based ...
Read more

ios - Change Storyboard View using Seague -

i have following code checks connection server, , depending on want change views if no connection found. nsstring *connect = [nsstring stringwithcontentsofurl:[nsurl urlwithstring:@"http://myserver.com"] encoding:nsutf8stringencoding error:nil]; if (connect == null) { [self performseguewithidentifier:@"network_failure" sender:self]; } else { // other code here } my problem not change views. have added storyboard segue between 2 views identifier of network_failure . not have navigation controller or that, problem? thanks help! no not problem. first of all, in objectivec exists nil object oriented null . must use that. so: if(connect == nil) or better: if(!connect) so due fact nil not same of null , probably code does't enter in if scope . you have been able discover breakpoint. anyway: be sure set trigger segue (line) 2 view controller , , name network_failure (that not best name. should instead view1toview2 ) as, m...
Read more