calvinlfer

package com.freckle.segmentation

import java.nio.charset.StandardCharsets.UTF_8
import java.util.concurrent.TimeUnit

import cats.effect._
import com.amazonaws.kinesis.deagg.RecordDeaggregator
import com.amazonaws.services.lambda.runtime.events.KinesisEvent
import com.amazonaws.services.lambda.runtime.{Context, RequestHandler}
import models._

calvinlfer

Developing an understanding of the FS2 Pull data type

In Pull[F, O, R], R is the return type. Pull represents a computation that emits some values on the Stream (of type O) and returns a new thing (R). In order to convert a Pull to a Stream, R must be Unit. This is because an FS2 Stream does not have the ability to terminate with a return value.

See here for the conversation

• Stream[F, O] is monadic over O which are the output values emitted
• Pull[F, O, R] is monadic over R which is used for stateful transformations

calvinlfer

import fs2._
import cats.effect._

import scala.concurrent.{ExecutionContext, Future}
import scala.concurrent.duration._
import scala.language.higherKinds

object UnderscoreFS2QueueDequeuePost extends App {
  implicit val ec: ExecutionContext =
    scala.concurrent.ExecutionContext.Implicits.global

calvinlfer

import cats.effect._
import fs2._
import fs2.async._

def log[F[_]: Sync, A](prefix: String): Pipe[F, A, A] =
  inputStream => inputStream.evalMap(a => Sync[F].delay {
    println(s"$prefix> $a")
    a
  })

calvinlfer

// Copyright(C) 2018 - John A. De Goes. All rights reserved.

package net.degoes.essentials

import java.time.{Instant, ZonedDateTime}

import scala.util.Try

object types {
  type ??? = Nothing

calvinlfer

// Copyright(C) 2018 - John A. De Goes. All rights reserved.

package net.degoes.abstractions

import scalaz._
import Scalaz._

import scala.language.higherKinds

object algebra {

calvinlfer

// Copyright(C) 2018 - John A. De Goes. All rights reserved.

package net.degoes.effects

import scalaz.zio._
import scalaz.zio.console._

import scala.annotation.tailrec
import scala.concurrent.duration._

calvinlfer

// Copyright(C) 2018 - John A. De Goes. All rights reserved.

package net.degoes.applications

import java.util.concurrent.ExecutorService

import scalaz.zio._
import scalaz.zio.console._
import scalaz.zio.interop.scalaz72._
import scalaz._

calvinlfer

  object fpdesign {
    /**
      * Business requirements
      * ---------------------
      * Loyalty Points management
      *
      * Entities (data)
      *   - Customer
      *   - Loyalty Points
      *   - Loyalty Point Account

calvinlfer

package com.github.calvin
import scalaz.zio._
import scalaz.zio.console._

object Main extends scalaz.zio.App {

  override def run(args: List[String]): IO[Nothing, ExitStatus] = {
    def promptForNumber: IO[Exception, Int] = {
      def toNumber(input: String): Option[Int] = {
        def isNumber(input: String): Boolean = (input.length == 1) && input.head.isDigit