Matt Parsons parsonsmatt

These links no longer work. Springer have pulled the free plug.

duplicates = multiple editions

	DROP DATABASE IF EXISTS animalsdb;
	CREATE DATABASE animalsdb;

	\c animalsdb;

	-- We're modeling the following Haskell datatype:
	--
	-- data Animal = Cat Name Age \| Dog Name OwnerId
	--
	-- We're going to factor the common 'Name' field into the animal table.

	instance YesodPersist App where
	type YesodPersistBackend App = SqlBackend
	runDB action = do
	master <- getYesod
	runSqlPool (hackTheReader action) $ appConnPool master

	newtype BenchmarkResults = BenchmarkResults [(Text,TimeSpec)]
	deriving Typeable
	type TypeMap = HashMap TypeRep Dynamic

	# Since a key-value store is a finite, discrete function, and functions
	# can be composed, then Hashes can be composed.
	#
	# The syntactic sugar for calling lambdas, accessing array values, and
	# other objects which have a #[] method allow composition of Hashes
	# with all sorts of objects and contexts with the same implementation.
	#
	# Play with it at https://eval.in/388458
	#
	class Hash

	{-# LANGUAGE DeriveFunctor #-}
	{-# LANGUAGE MultiParamTypeClasses #-}
	{-

	Explores Free Monads (DSLs) and Cofree Comonads (interpreters) and
	their relationship.

	Most of the code in this file comes from (1) below. Only minor
	modifications are made - semantics are preserved.

	-- Working through the Yorgey lectures on Applicatives for Haskell and trying to work out the homework...

	-- A parser for a value of type a is a function which takes a String
	-- represnting the input to be parsed, and succeeds or fails; if it
	-- succeeds, it returns the parsed value along with the remainder of
	-- the input.
	newtype Parser a = Parser { runParser :: String -> Maybe (a, String) }

	-- For example, 'satisfy' takes a predicate on Char, and constructs a
	-- parser which succeeds only if it sees a Char that satisfies the