Entries tagged with scala

Entry tags:

tuesday event

John De Goes is Programming Without Type Classes

Type classes have become a cornerstone of statically-typed functional programming, powering abstractions like monoid and monad. Yet, type classes often have generalized names, which don’t reflect their purpose in specific domains; and they incur higher learning costs, especially when emulated in languages without them.

In this presentation, John De Goes discusses the pros and cons of using type classes, and presents a systematic method for building powerful functional components that do not require type classes. Attendees will learn how to preserve the benefits of principled, algebraic functional programming, without forcing type classes on coworkers or users.

Entry tags:

scala

scala 3 for scala 2 programmers

Reference slides

https://tinyurl.com/scala2to3

Entry tags:

idiocracy,
scala

понедельничек

Юджин Йокота деплойнул sbt в jfrog, вместо чего-то там.

В результате по всей планете билды скальных продуктов сломаны.

Вот это заебись надежность. Я вообще не понимаю, как можно бесконтрольные апдейты устраивать.

Entry tags:

scala

regarding Scala types

Had a discussion yesterday. Basically, about this equality:

scala> "abc": Iterable[Char]
val res0: Iterable[Char] = abc

scala> List('a', 'b', 'c'): Iterable[Char]
val res1: Iterable[Char] = List(a, b, c)

scala> res0 == res1                                                                                                        
val res2: Boolean = true

No surprise, just making sure that it behaves as expected. Two projections are equal.

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а вот немножко логики

Вот простые два теста на Котлине.

    Stream.of<String>().forAll {   it.isEmpty() } shouldBe true
    Stream.of<String>().forAll {  !it.isEmpty() } shouldBe true

Не очень понятно, как это непрофессионалы воспримут. Моим студентам требуются усилия обычно.

Entry tags:

scala,
scrum

how to hire, a tutorial

Entry tags:

scala

munit

Послушал тут доклад на мадридском митапе, про munit - ну как-то не вижу смысла; junit надоел хуже горькой редьки, а этот не особо далеко ушел, только что stack trace highlighting. Я уж лучше specs2 продолжу использовать.

Или?

Entry tags:

scala

strange scala code

def x: { def k: Int } = new { def k: Int = 42 }

Entry tags:

scala

just figured

Just figured, `_` in Scala is an example of anaphora.

Entry tags:

scala

монокль

https://blog.fp-tower.com/monocle-3-a-peek-into-the-future/#1

Entry tags:

scala

Jon Pretty on Fury at ScalaBay

https://www.youtube.com/embed/o_8uw6BCliU

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here's the Https Server I wrote

https://github.com/vpatryshev/presheaf2/blob/master/src/main/scala/com/presheaf/http/HttpsServer.scala

See the readme at https://github.com/vpatryshev/presheaf2 for details.

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с ужасом обнаружил...

Что в ScalaZ ноль тестов для OptionT. Я им когда-то навалял тест для finger trees, ну и. Короче, за столько лет если не сбацали, так и все уже, наверно. Хм. Это я хотел поэкспериментировать. Потому что не совсем понимаю причин коммутирования (и могу привести простой контрпример). Пошел смотреть, как оно в typelevel/cats. In short. Have to use cats. Probably not. Will take a look at ZIO later.

Entry tags:

fp,
scala

SF Scala Video Channel

https://www.youtube.com/user/FunctionalTV

Entry tags:

scala,
еноты

пара заметок

Ночью приходил енот, помыл кошкину миску. Почему этого енота не записала камера, непонятно.

Regarding type parameters and member types. Say, you have trait T[X]{}. With a certain caveat, you may view it as a functor. If you have trait T { type X }. We have a partial mapping that, given a type, produces X (or not).

We can as well view both as binary relations between types (or profunctors, if we go to categories). One is an inverse of another.

So when you choose which one to prefer, mind the meaning of it.

(inspired by Compall's blog from 2015.

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about tagless-final

Juan Manuel talks

his slides

his code

John de Goes' opinion

(me: still struggling with all this)

Entry tags:

scala

I recommend this book

Li Haoyi, Hands-on Scala

https://www.handsonscala.com/

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come listen to my talk on topos logic implementation

https://www.meetup.com/SF-Types-Theorems-and-Programming-Languages/events/270634414/

Entry tags:

scala

seems like a compiler bug

Welcome to Scala 2.12.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_92).
Type in expressions for evaluation. Or try :help.

scala> def f(x: Int) = 10 + x -> "ok"
f: (x: Int)(Int, String)

scala> f(10)
res0: (Int, String) = (20,ok)

scala> def g(x: Int) = 20 + x → "oops"
:11: error: overloaded method value + with alternatives:
  (x: Double)Double 
  (x: Float)Float 
  (x: Long)Long 
  (x: Int)Int 
  (x: Char)Int 
  (x: Short)Int 
  (x: Byte)Int 
  (x: String)String
 cannot be applied to ((Int, String))
       def g(x: Int) = 20 + x → "oops"
                          ^

Entry tags:

categories,
scala

ok, done with Lawvere-Tierney topologies

https://github.com/vpatryshev/Categories/blob/master/src/main/scala/math/cat/topos/LawvereTopology.scala

That's in Grothendieck toposes, of course.