{"action":"created","issue":{"url":"https://api.github.com/repos/boostorg/hana/issues/221","labels_url":"https://api.github.com/repos/boostorg/hana/issues/221/labels{/name}","comments_url":"https://api.github.com/repos/boostorg/hana/issues/221/comments","events_url":"https://api.github.com/repos/boostorg/hana/issues/221/events","html_url":"https://github.com/boostorg/hana/issues/221","id":121789094,"number":221,"title":"[find_if] Predicates should be allowed to return an int_c.","user":{"login":"ricejasonf","id":2257044,"avatar_url":"https://avatars.githubusercontent.com/u/2257044?v=3","gravatar_id":"","url":"https://api.github.com/users/ricejasonf","html_url":"https://github.com/ricejasonf","followers_url":"https://api.github.com/users/ricejasonf/followers","following_url":"https://api.github.com/users/ricejasonf/following{/other_user}","gists_url":"https://api.github.com/users/ricejasonf/gists{/gist_id}","starred_url":"https://api.github.com/users/ricejasonf/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/ricejasonf/subscriptions","organizations_url":"https://api.github.com/users/ricejasonf/orgs","repos_url":"https://api.github.com/users/ricejasonf/repos","events_url":"https://api.github.com/users/ricejasonf/events{/privacy}","received_events_url":"https://api.github.com/users/ricejasonf/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/boostorg/hana/labels/bug","name":"bug","color":"fc2929"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":4,"created_at":"2015-12-11T20:50:18Z","updated_at":"2015-12-11T21:41:46Z","closed_at":null,"body":"I wanted to use hana::length as a predicate for `find_if` and `filter`, but it does not compile. Consider the following example.\r\n```\r\n#include<boost/hana.hpp>\r\n\r\nnamespace hana = boost::hana;\r\n\r\nint main()\r\n{\r\n  static_assert(hana::find_if(hana::make_tuple(\r\n      hana::make_tuple(),\r\n      hana::make_tuple(),\r\n      hana::make_tuple(hana::int_c<0>, hana::int_c<1>),\r\n      hana::make_tuple()), hana::length)\r\n        ==\r\n      hana::just(hana::make_tuple(hana::int_c<0>, hana::int_c<1>)), \"\");\r\n}\r\n```"},"comment":{"url":"https://api.github.com/repos/boostorg/hana/issues/comments/164054187","html_url":"https://github.com/boostorg/hana/issues/221#issuecomment-164054187","issue_url":"https://api.github.com/repos/boostorg/hana/issues/221","id":164054187,"user":{"login":"ricejasonf","id":2257044,"avatar_url":"https://avatars.githubusercontent.com/u/2257044?v=3","gravatar_id":"","url":"https://api.github.com/users/ricejasonf","html_url":"https://github.com/ricejasonf","followers_url":"https://api.github.com/users/ricejasonf/followers","following_url":"https://api.github.com/users/ricejasonf/following{/other_user}","gists_url":"https://api.github.com/users/ricejasonf/gists{/gist_id}","starred_url":"https://api.github.com/users/ricejasonf/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/ricejasonf/subscriptions","organizations_url":"https://api.github.com/users/ricejasonf/orgs","repos_url":"https://api.github.com/users/ricejasonf/repos","events_url":"https://api.github.com/users/ricejasonf/events{/privacy}","received_events_url":"https://api.github.com/users/ricejasonf/received_events","type":"User","site_admin":false},"created_at":"2015-12-11T21:41:46Z","updated_at":"2015-12-11T21:41:46Z","body":"I tried finding other functions that take a predicate with `grep -r 'holding a value convertible to a bool'`, but it doesn't return ANY results from hana's root. Is that generated? (found in `find_if` parameters pred)"}}