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(.module:
[lux #*]
[//
["." functor (#+ Functor)]])
(def: (list@fold f init xs)
(All [a b]
(-> (-> b a a) a (List b) a))
(case xs
#.Nil
init
(#.Cons x xs')
(list@fold f (f x init) xs')))
(def: (list@size xs)
(All [a] (-> (List a) Nat))
(loop [counter 0
xs xs]
(case xs
#.Nil
counter
(#.Cons _ xs')
(recur (inc counter) xs'))))
(def: (reverse xs)
(All [a]
(-> (List a) (List a)))
(list@fold (function (_ head tail) (#.Cons head tail))
#.Nil
xs))
(def: (as-pairs xs)
(All [a] (-> (List a) (List [a a])))
(case xs
(#.Cons x1 (#.Cons x2 xs'))
(#.Cons [x1 x2] (as-pairs xs'))
_
#.Nil))
(signature: #export (Monad m)
(: (Functor m)
&functor)
(: (All [a]
(-> a (m a)))
wrap)
(: (All [a]
(-> (m (m a)) (m a)))
join))
(def: _cursor Cursor ["" 0 0])
(macro: #export (do tokens state)
{#.doc (doc "Macro for easy concatenation of monadic operations."
(do monad
[y (f1 x)
z (f2 z)]
(wrap (f3 z))))}
(case tokens
(#.Cons monad (#.Cons [_ (#.Tuple bindings)] (#.Cons body #.Nil)))
(if (|> bindings list@size .int ("lux i64 %" +2) ("lux i64 =" +0))
(let [g!_ (: Code [_cursor (#.Identifier ["" " _ "])])
g!map (: Code [_cursor (#.Identifier ["" " map "])])
g!join (: Code [_cursor (#.Identifier ["" " join "])])
body' (list@fold (: (-> [Code Code] Code Code)
(function (_ binding body')
(let [[var value] binding]
(case var
[_ (#.Tag ["" "let"])]
(` (let (~ value) (~ body')))
_
(` (|> (~ value) ((~ g!map) (function ((~ g!_) (~ var)) (~ body'))) (~ g!join)))
))))
body
(reverse (as-pairs bindings)))]
(#.Right [state (#.Cons (` ({(~' @)
({[(~ g!map) (~' wrap) (~ g!join)]
(~ body')}
(~' @))}
(~ monad)))
#.Nil)]))
(#.Left "'do' bindings must have an even number of parts."))
_
(#.Left "Wrong syntax for 'do'")))
(def: #export (seq monad)
{#.doc "Run all the monadic values in the list and produce a list of the base values."}
(All [M a]
(-> (Monad M) (List (M a))
(M (List a))))
(let [(^open "!@.") monad]
(function (recur xs)
(case xs
#.Nil
(!@wrap #.Nil)
(#.Cons x xs')
(|> x
(!@map (function (_ _x)
(!@map (|>> (#.Cons _x)) (recur xs'))))
!@join)))))
(def: #export (map monad f)
{#.doc "Apply a monadic function to all values in a list."}
(All [M a b]
(-> (Monad M) (-> a (M b)) (List a)
(M (List b))))
(let [(^open "!@.") monad]
(function (recur xs)
(case xs
#.Nil
(!@wrap #.Nil)
(#.Cons x xs')
(|> (f x)
(!@map (function (_ _x)
(!@map (|>> (#.Cons _x)) (recur xs'))))
!@join)))))
(def: #export (filter Monad<!> f)
{#.doc "Filter the values in a list with a monadic function."}
(All [! a b]
(-> (Monad !) (-> a (! Bit)) (List a)
(! (List a))))
(let [(^open "!@.") Monad<!>]
(function (recur xs)
(case xs
#.Nil
(!@wrap #.Nil)
(#.Cons head xs')
(|> (f head)
(!@map (function (_ verdict)
(!@map (function (_ tail)
(if verdict
(#.Cons head tail)
tail))
(recur xs'))))
!@join)))))
(def: #export (fold monad f init xs)
{#.doc "Fold a list with a monadic function."}
(All [M a b]
(-> (Monad M) (-> b a (M a)) a (List b)
(M a)))
(case xs
#.Nil
(:: monad wrap init)
(#.Cons x xs')
(do monad
[init' (f x init)]
(fold monad f init' xs'))))
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