What does comparable mean in Elm? -

-

i'm having trouble understanding comparable in elm. elm seems confused am.

on repl: 

> f1 = (<) <function> : comparable -> comparable -> bool

so f1 accepts comparables.

> "a" "a" : string > f1 "a" "b" true : bool

so seems string comparable.

> f2 = (<) 1 <function> : comparable -> bool

so f2 accepts comparable.

> f2 "a" infer type of values flowing through program, see conflict between these 2 types:      comparable      string

so string is , is not comparable?
why type of f2 not number -> bool? other comparables can f2 accept?

normally when see type variable in type in elm, variable unconstrained. when supply of specific type, variable gets replaced specific type:

-- says have function: foo : -> -> -> int -- once give value actual type foo, occurences of `a` replaced type: value : float foo value : float -> float -> int

comparable type variable built-in special meaning. meaning match against "comparable" types, int, string , few others. otherwise should behave same. think there little bug in type system, given get:

> f2 "a" infer type of values flowing through program, see conflict between these 2 types:      comparable      string

if bug weren't there, get:

> f2 "a" infer type of values flowing through program, see conflict between these 2 types:      int      string

edit: opened issue bug


Comments

Post a Comment

Popular posts from this blog

yii2 - Yii 2 Running a Cron in the basic template -

-
i have seen instructions on running cron in advanced template, cant figure out how on basic template. have following controller in basic controllers folder. <?php namespace app\controllers; use yii\console\controller; /** * cron controller */ class croncontroller extends controller { public function actionindex() { echo "cron service runnning"; } public function actionmail($to) { echo "sending mail " . $to; } } i have navigated root of application , tried these comands yii cron php yii cron im getting unknown comand "cron" i know old question failed find actual answer this. if @ code yii exec file you'll notice requires /common/config/aliases.php file console/config/main.php. can naturally change these or copy on these advanced template. hope solves problem wanting same thing.
Read more

asp.net - 'System.Web.HttpContext' does not contain a definition for 'GetOwinContext' Mystery -

-
i realize question might seem trivial some, it's these types of things find myself fighting quite bit , want make sense of despite seeming losing battle in .net (for me anyway). so, if following: using system.web; ... applicationuser user = system.web.httpcontext.getowincontext().getusermanager<applicationusermanager>().findbyid(system.web.httpcontext.user.identity.getuserid()); that produces error in title , red getowincontext() , error cannot resolve symbol 'getowincontext()' however, if following (remove system.web in front of httpcontext ), works expected (or @ least no errors): using system.web; ... applicationuser user = httpcontext.getowincontext().getusermanager<applicationusermanager>().findbyid(system.web.httpcontext.user.identity.getuserid()); however, if (same line that's working using system.web commented out): //using system.web; ... applicationuser user = httpcontext.getowincontext().getusermana...
Read more

mercurial graft feature, can it copy? -

-
there new feature in mercurial 3, called 'graft' (graft local). job of moving change-set different branch. is there way "copy" change-set branch? i interested in in moving stuff qa branch production branch, still need code reside in qa. want copy. found , have tried few things, maybe it'll become clear more tinkering , reading... does have better way of 'cherry picking' change-sets move cross branch (or trunk)??? graft copies changesets, doesn't move them. hg graft (emphasis mine): this command uses mercurial's merge logic copy individual changes other branches without merging branches in history graph. known 'backporting' or 'cherry-picking' . default, graft copy user, date, , description source changesets.
Read more