Sam Vervaeck samvv

Monoids in Haskell, an Introduction

Why should programmers care about Monoids? Because Monoids are a common pattern that shows up over and over in programming. And when patterns show up, we can abstract them and leverage work we've done in the past. This allows us to quickly develop solutions on top of proven, stable code.

Add Commutative Property to a Monoid (Commutative Monoid) and you have something that can be executed in parallel. With the end of Moore's Law, parallelism is our only hope to increasing processing speeds.

What follows is what I've learned after studying Monoids. It is hardly complete, but hopefully will prove to be helpful as an introduction for others.

Monoid Lineage

Typing Haskell in Haskell

MARK P. JONES

Pacific Software Research Center

Department of Computer Science and Engineering

Oregon Graduate Institute of Science and Technology

	(* Compile with:
	$ ocamlfind ocamlc -package angstrom,stdio -linkpkg tychk.ml -o tychk
	Example use:
	$ ./tychk <<EOF
	> let f = (fun x -> x) : forall a. a -> a
	> in f f
	> EOF
	input : forall a. a -> a
	*)

	--- Actions ---
	$Copy <M-C>
	$Cut <M-X> <S-Del>
	$Delete <Del> <BS> <M-BS>
	$LRU
	$Paste <M-V>
	$Redo <M-S-Z> <A-S-BS>
	$SearchWeb <A-S-G>
	$SelectAll <M-A>
	$Undo <M-Z>