beezee

new oq, qr, n, req. (Init[oq, req] | S[oq, qr] | I[qr, n] | F[n])
S[oq, qr] := oq(req).new query.S_query[qr, query]
S_query[qr, query] := qr<query>.S[qr, qr]
I[qr, n] := qr(query).new response.I_notice[qr, n, response]
I_notice[qr, n, response] := n<response>.I_respond[qr, n, response]
I_respond[qr, n, resp] := qr<resp>.I[qr, n]
F[n] := n(resp).F_recv[n]
F_recv[n] := τ.F[n]
Init[qr, req] := qr<req>

neko-kai

package quantified

import cats.Monad

import scala.language.implicitConversions

/**
  * C[_] constraint applied to type F[_, _] quantified in first parameter, i.e.
  *
  * {{{

hobwekiva

sealed trait Decidable[+Proof]
final case class Yes[Proof](proof: Proof) extends Decidable[Proof]
final case object No extends Decidable[Nothing]

sealed trait List[+A] {
  def nonEmpty: Decidable[this.type <:< ::[A]]
  def ::[AA >: A](value: AA): ::[AA] = new ::[AA](value, this)
}
final case object Nil extends List[Nothing] {
  def nonEmpty: Decidable[this.type <:< ::[Nothing]] = No

gvanrossum

LIMIT = 5
BOUND = 'object'

def prelude(limit: int, bound: str) -> None:
    print('from typing import Callable, Iterable, Iterator, Tuple, TypeVar, overload')
    print('Ts = TypeVar(\'Ts\', bound={bound})'.format(bound=bound))
    print('R = TypeVar(\'R\')')
    for i in range(LIMIT):
        print('T{i} = TypeVar(\'T{i}\', bound={bound})'.format(i=i+1, bound=bound))

djspiewak

Explaining Miles's Magic

Miles Sabin recently opened a pull request fixing the infamous SI-2712. First off, this is remarkable and, if merged, will make everyone's life enormously easier. This is a bug that a lot of people hit often without even realizing it, and they just assume that either they did something wrong or the compiler is broken in some weird way. It is especially common for users of scalaz or cats.

But that's not what I wanted to write about. What I want to write about is the exact semantics of Miles's fix, because it does impose some very specific assumptions about the way that type constructors work, and understanding those assumptions is the key to getting the most of it his fix.

For starters, here is the sort of thing that SI-2712 affects:

def foo[F[_], A](fa: F[A]): String = fa.toString

runarorama

sealed trait Interact[A]

case class Ask(prompt: String)
  extends Interact[String]

case class Tell(msg: String)
  extends Interact[Unit]

trait Monad[M[_]] {
  def pure[A](a: A): M[A]

tsiege

ANNOUNCEMENT

I have moved this over to the Tech Interview Cheat Sheet Repo and has been expanded and even has code challenges you can run and practice against!






\

jbrowning

# The $provide service is used to override an injected dependency

# Bad - results in Error: [ng:areq] Argument 'fn' is not a function, got Object
module 'someModule', ($provide) ->
  $provide.value "SomeService", SomeMock

# Good
module 'someModule', ($provide) ->
  $provide.value "SomeService", SomeMock
  null

mmizutani

import com.lmax.disruptor.dsl.Disruptor
import java.util.concurrent.Executors
import com.lmax.disruptor._

case class ValueEvent(var value: Long)

case class ValueEventTranslator(value: Long) extends EventTranslator[ValueEvent] {
  def translateTo(event: ValueEvent, sequence: Long) = {
    event.value = value
    event

timoyuen

import com.lmax.disruptor.dsl.Disruptor
import java.util.concurrent.Executors
import com.lmax.disruptor._

case class ValueEvent(var value: Long)

case class ValueEventTranslator(value: Long) extends EventTranslator[ValueEvent] {
  def translateTo(event: ValueEvent, sequence: Long) = {
    event.value = value
    event