Romain Revol rrevol

Category theory jargon cheat sheet

A primer/refresher on the category theory concepts that most commonly crop up in conversations about Scala or FP. (Because it's embarassing when I forget this stuff!)

I'll be assuming Scalaz imports in code samples, and some of the code may be pseudo-Scala.

Functor

A functor is something that supports map.

	import org.apache.flink.streaming.api.functions.source.SourceFunction
	import org.apache.flink.streaming.api.scala.{StreamExecutionEnvironment, _}

	object FlinkDeadlockTest {
	val MAX_LOOP_NB = 10

	def main(args: Array[String]): Unit = {
	val env = StreamExecutionEnvironment.getExecutionEnvironment
	env.addSource(new SourceFunction[Int] {
	var goOn = true

	import AVFoundation
	import Foundation



	// The single FM synthesizer instance.
	private let gFMSynthesizer: FMSynthesizer = FMSynthesizer()

	public class FMSynthesizer {

	import java.util.*;
	import java.util.function.*;
	import rx.Observable;
	import rx.functions.Func1;
	import rx.observers.TestSubscriber;

	import static rx.Observable.*;
	import static rx.internal.util.UtilityFunctions.identity;
	import static rx.schedulers.Schedulers.*;

	import java.util.*;
	import java.util.concurrent.*;
	import com.google.common.cache.Cache;
	import com.google.common.cache.CacheBuilder;
	import com.google.common.cache.CacheStats;

	import static com.google.common.base.Preconditions.checkState;
	import static com.google.common.base.Throwables.propagate;
	import static java.util.concurrent.Executors.*;