| package fpmax | |
| import scala.util.Try | |
| import scala.io.StdIn.readLine | |
| object App0 { | |
| def main: Unit = { | |
| println("What is your name?") | |
| val name = readLine() |
Copyright © 2016-2018 Fantasyland Institute of Learning. All rights reserved.
A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.
val square : Int => Int = x => x * x
bin/kafka-topics.sh --zookeeper localhost:2181 --list
bin/kafka-topics.sh --zookeeper localhost:2181 --describe --topic mytopic
bin/kafka-topics.sh --zookeeper localhost:2181 --alter --topic mytopic --config retention.ms=1000
... wait a minute ...
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
Note: This was written using elasticsearch 0.9.
Elasticsearch will automatically create an index (with basic settings and mappings) for you if you post a first document:
$ curl -X POST 'http://localhost:9200/thegame/weapons/1' -d \
'{
"_id": 1,