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## Copyright (c) Eduardo Julian. All rights reserved.
## This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
## If a copy of the MPL was not distributed with this file,
## You can obtain one at http://mozilla.org/MPL/2.0/.
(;module:
lux
["F" ../functor]
[lux/data/coll/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))
## [Syntax]
(macro: #export (be tokens state)
{#;doc (doc "A co-monadic parallel to the \"do\" macro."
(let [square (lambda [n] (i.* n n))]
(be CoMonad<Stream>
[inputs (iterate i.inc 2)]
(square (head inputs)))))}
(case tokens
(#;Cons comonad (#;Cons [_ (#;TupleS bindings)] (#;Cons body #;Nil)))
(let [g!@ (: AST [["" -1 -1] (#;SymbolS ["" "@"])])
g!map (: AST [["" -1 -1] (#;SymbolS ["" " map "])])
g!split (: AST [["" -1 -1] (#;SymbolS ["" " split "])])
body' (fold (: (-> [AST AST] AST AST)
(lambda [binding body']
(let [[var value] binding]
(case var
[_ (#;TagS ["" "let"])]
(` (let (~ value) (~ body')))
_
(` (|> (~ value) (~ g!split) ((~ g!map) (lambda [(~ var)] (~ body')))))
))))
body
(reverse (as-pairs bindings)))]
(#;Right [state (#;Cons (` (;_lux_case (~ comonad)
(~ g!@)
(;_lux_case (~ g!@)
{#functor {#F;map (~ g!map)} #unwrap (~' unwrap) #split (~ g!split)}
(~ body'))))
#;Nil)]))
_
(#;Left "Wrong syntax for be")))
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