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|
(.using
[library
[lux (.except pattern only)
[abstract
[functor (.only Functor)]
[comonad (.only CoMonad)]]
[control
["//" continuation (.only Cont)]
["<>" parser (.only)
["<[0]>" code (.only Parser)]]]
[data
["[0]" bit]
[collection
["[0]" list ("[1]#[0]" monad)]]]
[macro (.only with_symbols)
[syntax (.only syntax:)]
["[0]" code]]
[math
[number
["n" nat]]]]])
(type: .public (Stream a)
(Cont [a (Stream a)]))
(def: .public (iterations step init)
(All (_ a b)
(-> (-> a [a b]) a (Stream b)))
(let [[next x] (step init)]
(//.pending [x (iterations step next)])))
(def: .public (repeated x)
(All (_ a)
(-> a (Stream a)))
(//.pending [x (repeated x)]))
(def: .public (cycle [start next])
(All (_ a)
(-> [a (List a)] (Stream a)))
(loop (again [head start
tail next])
(//.pending [head (case tail
{.#End}
(again start next)
{.#Item head' tail'}
(again head' tail'))])))
(template [<name> <return>]
[(def: .public (<name> stream)
(All (_ a) (-> (Stream a) <return>))
(let [[head tail] (//.result stream)]
<name>))]
[head a]
[tail (Stream a)]
)
(def: .public (item idx stream)
(All (_ a) (-> Nat (Stream a) a))
(let [[head tail] (//.result stream)]
(case idx
0 head
_ (item (-- idx) tail))))
(template [<taker> <dropper> <pred_type> <pred_test> <pred_step> <post_test>]
[(def: .public (<taker> pred xs)
(All (_ a)
(-> <pred_type> (Stream a) (List a)))
(let [[x xs'] (//.result xs)]
(if (<post_test> <pred_test>)
(partial_list x (<taker> <pred_step> xs'))
(list))))
(def: .public (<dropper> pred xs)
(All (_ a)
(-> <pred_type> (Stream a) (Stream a)))
(let [[x xs'] (//.result xs)]
(if (<post_test> <pred_test>)
(<dropper> <pred_step> xs')
xs)))]
[while until (-> a Bit) (pred x) pred |>]
[first after Nat (n.= 0 pred) (-- pred) not]
)
(template [<splitter> <pred_type> <pred_test> <pred_step>]
[(def: .public (<splitter> pred xs)
(All (_ a)
(-> <pred_type> (Stream a) [(List a) (Stream a)]))
(let [[x xs'] (//.result xs)]
(if <pred_test>
[(list) xs]
(let [[tail next] (<splitter> <pred_step> xs')]
[{.#Item [x tail]} next]))))]
[split_when (-> a Bit) (pred x) pred]
[split_at Nat (n.= 0 pred) (-- pred)]
)
(def: .public (only predicate stream)
(All (_ a) (-> (-> a Bit) (Stream a) (Stream a)))
(let [[head tail] (//.result stream)]
(if (predicate head)
(//.pending [head (only predicate tail)])
(only predicate tail))))
(def: .public (partition left? xs)
(All (_ a) (-> (-> a Bit) (Stream a) [(Stream a) (Stream a)]))
[(..only left? xs)
(..only (bit.complement left?) xs)])
(implementation: .public functor
(Functor Stream)
(def: (each f fa)
(let [[head tail] (//.result fa)]
(//.pending [(f head) (each f tail)]))))
(implementation: .public comonad
(CoMonad Stream)
(def: functor ..functor)
(def: out head)
(def: (disjoint wa)
(let [[head tail] (//.result wa)]
(//.pending [wa (disjoint tail)]))))
(syntax: .public (pattern [patterns (<code>.form (<>.many <code>.any))
body <code>.any
branches (<>.some <code>.any)])
(with_symbols [g!stream]
(let [body+ (` (let [(~+ (|> patterns
(list#each (function (_ pattern)
(list (` [(~ pattern) (~ g!stream)])
(` ((~! //.result) (~ g!stream))))))
list#conjoint))]
(~ body)))]
(in (partial_list g!stream body+ branches)))))
|
