Monads

monads.clj

; 
;   Monads
;   ======
; 
; * Without monads "pure" functional programming could be very impractical, Hack!
; * You can build environments that support exactly the features that you want
; * Functional able todo IO
; * Function Composition: LINQ, Unix Pipes
; * Good for control tracking of things
; * Encapsulating two things: 
;    - control flow (Maybe, Error, List, Continuation, parser monads) 
;    - state propagation (State, Reader, Writer, IO).
;
; Sample:
; 
;

;;; Monads ins Clojure  1   ;;; Function Composition
(defn triple[n](* 3 n))     ;;; function that triple a number - F1
(def inc3(comp triple inc)) ;;; F2 must produce a result that f1 can handle
(inc3 3)                    ;;; result is 12. R: inc 3 == 4, 4 * 3  == 12


;;; Monads ins Clojure  2               ;;; The Sequence Monad(Haskell 3 parts, types sing, 2 functions) 
;;;                                     ;;; Since clojure is dynamic type we just need 2 functions
;;;					;;; m-result and m-bind this are standard names										
;;;                                     ;;; monadic-values: (4 6)  monadic-functions: increase

(defn increase[x](list (+ x 1)(+ x 2))  ;;; receive a int and create a list with int+1 and int+2
(def  m-result list)                    ;;; create a list with a int
(defn m-bind[v f](mapcat f v))          ;;; Monadic bind call the value(list of int) into increase
(m-bind (m-result 4) increase)          ;;; (5 6)
	

; Resources:
; 
; http://marijnhaverbeke.nl/monad.html
; http://www.reddit.com/r/programming/comments/p66e/are_monads_actually_used_in_anything_except
; http://homepages.inf.ed.ac.uk/wadler/papers/marktoberdorf/baastad.pdf
; http://www.reddit.com/r/programming/tb/oq3m
; http://www.infoq.com/presentations/Monads-Made-Easy
; http://www.cas.mcmaster.ca/~carette/pa_monad/
; http://www.reddit.com/r/programming/comments/ox6s/ask_reddit_what_the_hell_are_monads/coxiv