Difference between revisions of "Monad"

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Implementations of monads in other languages.
 
Implementations of monads in other languages.
   
* [http://www-static.cc.gatech.edu/~yannis/fc++/FC++.1.5/monad.h C++]
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* [http://www-static.cc.gatech.edu/~yannis/fc++/FC++.1.5/monad.h C++], [http://www-static.cc.gatech.edu/~yannis/fc++/New1.5/lambda.html#monad doc]
 
* [http://cratylus.freewebspace.com/monads-in-javascript.htm JavaScript]
 
* [http://cratylus.freewebspace.com/monads-in-javascript.htm JavaScript]
 
* [http://www.ccs.neu.edu/home/dherman/code/monads/JavaMonads.tar.gz Java] (tar.gz)
 
* [http://www.ccs.neu.edu/home/dherman/code/monads/JavaMonads.tar.gz Java] (tar.gz)
 
* [http://permalink.gmane.org/gmane.comp.lang.concatenative/1506 Joy]
 
* [http://permalink.gmane.org/gmane.comp.lang.concatenative/1506 Joy]
 
* [http://sleepingsquirrel.org/monads/monads.lisp Lisp]
 
* [http://sleepingsquirrel.org/monads/monads.lisp Lisp]
* [http://www.cas.mcmaster.ca/~carette/pa_monad/ OCaml]
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* [http://www.cas.mcmaster.ca/~carette/pa_monad/ OCaml], [https://mailman.rice.edu/pipermail/metaocaml-users-l/2005-March/000057.html more], [http://www.pps.jussieu.fr/~beffara/darcs/pivm/caml-vm/monad.mli also]
 
* [http://sleepingsquirrel.org/monads/monads.html Perl]
 
* [http://sleepingsquirrel.org/monads/monads.html Perl]
 
* [http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/439361 Python]
 
* [http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/439361 Python]
 
* [http://logic.csci.unt.edu/tarau/research/PapersHTML/monadic.html Prolog]
 
* [http://logic.csci.unt.edu/tarau/research/PapersHTML/monadic.html Prolog]
 
* [http://moonbase.rydia.net/mental/writings/programming/monads-in-ruby/00introduction.html Ruby]
 
* [http://moonbase.rydia.net/mental/writings/programming/monads-in-ruby/00introduction.html Ruby]
* [http://okmij.org/ftp/Scheme/monad-in-Scheme.html Scheme]
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* [http://okmij.org/ftp/Scheme/monad-in-Scheme.html Scheme], [http://www.ccs.neu.edu/home/dherman/research/tutorials/monads-for-schemers.txt also]
 
* [http://okmij.org/ftp/Computation/monadic-shell.html The Unix Shell]
 
* [http://okmij.org/ftp/Computation/monadic-shell.html The Unix Shell]
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* [http://clean.cs.ru.nl/Download/Download_Libraries/Std_Env/StdFunc/stdfunc.html Clean] State monad
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* [http://lambda-the-ultimate.org/node/1136#comment-12448 Miranda]
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* [http://scala.epfl.ch/examples/files/simpleInterpreter.html Scala], also [http://scala.epfl.ch/examples/files/callccInterpreter.html continuation monad]
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  +
Unfinished:
  +
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* [http://slate.tunes.org/repos/main/src/unfinished/monad.slate Slate]
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* [http://wiki.tcl.tk/14295 Parsing], [http://wiki.tcl.tk/13844 Maybe and Error] in Tcl
   
 
And possibly there exist:
 
And possibly there exist:
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Please add them if you know of other implementations.
 
Please add them if you know of other implementations.
  +
  +
[http://lambda-the-ultimate.org/node/1136 Collection of links to monad implementations in various languages.] on [http://lambda-the-ultimate/ Lambda The Ultimate].
   
 
==Interesting monads==
 
==Interesting monads==

Revision as of 19:29, 3 November 2006

Monad class (base)
import Control.Monad

The Monad class is defined like this:

class Monad m where
  (>>=) :: m a -> (a -> m b) -> m b
  (>>) :: m a -> m b -> m b
  return :: a -> m a
  fail :: String -> m a

All instances of Monad should obey:

return a >>= k  =  k a
m >>= return  =  m
m >>= (\x -> k x >>= h)  =  (m >>= k) >>= h

See this intuitive explanation of why they should obey the Monad laws.

Any Monad can be made a Functor by defining

fmap ab ma = ma >>= (return . ab)

However, the Functor class is not a superclass of the Monad class. See Functor hierarchy proposal.

Monad Tutorials

Monads are known for being deeply confusing to lots of people, so there are plenty of tutorials specifically related to monads. Each takes a different approach to Monads, and hopefully everyone will find something useful.

Monad Reference Guides

An explanation of the basic Monad functions, with examples, can be found in the reference guide A tour of the Haskell Monad functions, by Henk-Jan van Tuyl.

Monads in other languages

Implementations of monads in other languages.

Unfinished:

And possibly there exist:

  • Standard ML (via modules?)
  • Clean (via uniquness types?)

Please add them if you know of other implementations.

Collection of links to monad implementations in various languages. on Lambda The Ultimate.

Interesting monads

A list of monads for various evaluation strategies and games:

There are many more interesting instance of the monad abstraction out there. Please add them as you come across each species.