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(;module:
lux
["F" //functor]
(lux/data/coll [list "list/" Fold<List>]))
## [Signatures]
(sig: #export (CoMonad w)
{#;doc "CoMonads are the opposite/complement to monads.
CoMonadic structures are often infinite in size and built upon lazily-evaluated functions."}
(: (F;Functor w)
functor)
(: (All [a]
(-> (w a) a))
unwrap)
(: (All [a]
(-> (w a) (w (w a))))
split))
## [Types]
(type: #export (CoFree F a)
{#;doc "The CoFree CoMonad."}
[a (F (CoFree F a))])
## [Syntax]
(def: _cursor Cursor ["" +0 +0])
(macro: #export (be tokens state)
{#;doc (doc "A co-monadic parallel to the \"do\" macro."
(let [square (function [n] (i.* n n))]
(be CoMonad<Stream>
[inputs (iterate i.inc 2)]
(square (head inputs)))))}
(case tokens
(#;Cons comonad (#;Cons [_ (#;Tuple bindings)] (#;Cons body #;Nil)))
(if (|> bindings list;size (n.% +2) (n.= +0))
(let [g!map (: Code [_cursor (#;Symbol ["" " map "])])
g!split (: Code [_cursor (#;Symbol ["" " split "])])
body' (list/fold (: (-> [Code Code] Code Code)
(function [binding body']
(let [[var value] binding]
(case var
[_ (#;Tag ["" "let"])]
(` (let (~ value) (~ body')))
_
(` (|> (~ value) (~ g!split) ((~ g!map) (function [(~ var)] (~ body')))))
))))
body
(list;reverse (list;as-pairs bindings)))]
(#;Right [state (#;Cons (` ("lux case" (~ comonad)
{(~' @)
("lux case" (~' @)
{{#functor {#F;map (~ g!map)} #unwrap (~' unwrap) #split (~ g!split)}
(~ body')})}))
#;Nil)]))
(#;Left "'be' bindings must have an even number of parts."))
_
(#;Left "Wrong syntax for 'be'")))
|
