scalaz - fs2 Task.start vs async -


i have 2 tasks:

  val t = system.currenttimemillis()    def first: fs2.task[int] = fs2.task.fromfuture(future.successful {     println(s"${ system.currenttimemillis() - t} - first")     thread.sleep(100)     1   })    def second: fs2.task[int] = fs2.task.fromfuture(future.successful {     println(s"${system.currenttimemillis() - t} - second")     thread.sleep(200)     2   })

i want start them in parallel, , run function on results in end (pretty i'd vs applicative map2). works fine:

  val comb = {     ta ← fs2.task.start(first)     tb ← fs2.task.start(second)     ← ta     b ← tb   } yield {     println("complete")     + b   }  comb.unsaferun()

output: 164 - first 164 - second

it bit tedious write line in comprehension every time. suprise neither

import fs2.interop.scalaz._ import scalaz.syntax.applicative._ val comb2 = (first |@| second) {_ + _}

output: 197 - first 318 - second

nor 

  val comb1 = {     ← first.async     b ← second.async   } yield {     + b   }

output: 202 - first 323 - second

worked. while in first case tasks started simultaneuosly, in latter 2, began 1 after another.

what missing? reading implementation of async understood, intent make first snippet syntactically attractive, cant believe there bug, possibly misuse async?


Comments

Post a Comment

Popular posts from this blog

c# - Update a combobox from a presenter (MVP) -

i using mvp in project, new in mvp. have 2 comboboxes. when select option in combobox, combobox should filled new data. this action in presenter. view 'view1' in presenter, , introduced combobox1 , combobox2 properties in 'view1', because need 'datasource', 'displaymember', 'valuemember' , 'refresh()' in method below. but, when using pattern, enough send property like public string combobox2 { { return combobox1.selectedvalue.tosstring(); } } into presenter not whole combobox. how can solve problem? public void onselectedindexchangedcombobox1() { if (view1.combobox1.selectedindex == -1) { return; } datatable dt = tools.getdatatable("a path"); var query = (from o in dt.asenumerable() o.field<string>("afield") == farmerview.combobox1.selectedvalue.tostring() orderby o.field<string>("anotherfield") select...
Read more

android - Unable to generate FCM token from dynamically instantiated Firebase -

our business logic requires instantiate firebase during runtime. fetch firebase credentials (app id, api key etc.) default firebase location after knowing user's public key , create firebase instance using credentials. this means there 2 firebase instances used within app: the default "index" firebase gives credentials second the actual firebase intend use point forward the second firebase initialised this: firebaseapp app = firebaseapp.initializeapp(<context>, <options>, <app_label>); our problem traditional method of retrieving fcm token using firebaseinstanceidservice , ontokenrefresh() fails since ontokenrefresh() method called first firebase instance. directly calling string token = firebaseinstanceid.getinstance(app).gettoken(); returns null never ready when called. have tried polling test if token generated @ point. no luck. how can generate fcm token reliably firebase instance instantiated during runtime? i...
Read more

How to put a lock and transaction on table using spring 4 or above using jdbcTemplate and annotations like @Transactional? -

i trying put lock on table while writing on table , if happened in between roll-back . trying convert below code lock table test_g1 read; lock table test_g write; -- begin; start transaction; insert test_g1 values(143); insert test_g values(145); select * test_g1; select * test_g; rollback; select * test_g; unlock tables; how convert above code @transactional spring jdbctemplate code? @transactional(rollbackfor={dataaccessexception.class}) public void test(){ jdbctemplate.execute("insert test1 (id, nam) values (4, 'a')"); throw new dataaccessexception("error") { }; } here trying throw error, insert statement should rollback it's not happening . thanks edit-1 attaching code , doing in jdbcdaoimpl.java , mentioned problem comment above test() . app.java package com.cgiri.javabrains.spring4; import org.springframework.beans.factory.annotation.autowired; import org.springframework.context.applic...
Read more