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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
(lux (data (struct [list "" Monad<List> Fold<List> "List/" Monoid<List>]
[tree #+ Tree]
[stack #+ Stack]))
[compiler]
(macro [ast]
["s" syntax #+ syntax: Syntax])))
## Adapted from the clojure.zip namespace in the Clojure standard library.
## [Types]
(type: #export (Zipper a)
{#parent (Maybe (Zipper a))
#lefts (Stack (Tree a))
#rights (Stack (Tree a))
#node (Tree a)})
## [Values]
(def: #export (from-tree tree)
(All [a] (-> (Tree a) (Zipper a)))
{#parent #;None
#lefts stack;empty
#rights stack;empty
#node tree})
(def: #export (to-tree zipper)
(All [a] (-> (Zipper a) (Tree a)))
(get@ #node zipper))
(def: #export (value zipper)
(All [a] (-> (Zipper a) a))
(|> zipper (get@ #node) (get@ #tree;value)))
(def: #export (children zipper)
(All [a] (-> (Zipper a) (List (Tree a))))
(|> zipper (get@ #node) (get@ #tree;children)))
(def: #export (branch? zipper)
(All [a] (-> (Zipper a) Bool))
(|> zipper children list;empty? not))
(def: #export (leaf? zipper)
(All [a] (-> (Zipper a) Bool))
(|> zipper branch? not))
(def: #export (parent zipper)
(All [a] (-> (Zipper a) (Maybe (Zipper a))))
(get@ #parent zipper))
(def: #export (down zipper)
(All [a] (-> (Zipper a) (Zipper a)))
(case (children zipper)
#;Nil
zipper
(#;Cons chead ctail)
{#parent (#;Some zipper)
#lefts stack;empty
#rights ctail
#node chead}))
(def: #export (up zipper)
(All [a] (-> (Zipper a) (Zipper a)))
(case (get@ #parent zipper)
#;None
zipper
(#;Some parent)
(|> parent
(update@ #node (: (-> (Tree ($ +0)) (Tree ($ +0)))
(lambda [node]
(set@ #tree;children (List/append (list;reverse (get@ #lefts zipper))
(#;Cons (get@ #node zipper)
(get@ #rights zipper)))
node)))))))
(def: #export (root zipper)
(All [a] (-> (Zipper a) (Zipper a)))
(loop [zipper zipper]
(case (get@ #parent zipper)
#;None zipper
(#;Some _) (recur (up zipper)))))
(do-template [<one-name> <all-name> <side> <op-side>]
[(def: #export (<one-name> zipper)
(All [a] (-> (Zipper a) (Zipper a)))
(case (get@ <side> zipper)
#;Nil
zipper
(#;Cons next side')
(|> zipper
(update@ <op-side> (lambda [op-side]
(#;Cons (get@ #node zipper) op-side)))
(set@ <side> side')
(set@ #node next))))
(def: #export (<all-name> zipper)
(All [a] (-> (Zipper a) (Zipper a)))
(fold (lambda [_] <one-name>) zipper (get@ <side> zipper)))]
[right rightmost #rights #lefts]
[left leftmost #lefts #rights]
)
(def: #export (set value zipper)
(All [a] (-> a (Zipper a) (Zipper a)))
(set@ [#node #tree;value] value zipper))
(def: #export (update f zipper)
(All [a] (-> (-> a a) (Zipper a) (Zipper a)))
(update@ [#node #tree;value] f zipper))
(def: #export (prepend-child value zipper)
(All [a] (-> a (Zipper a) (Zipper a)))
(update@ [#node #tree;children]
(lambda [children]
(#;Cons (tree;tree ($ +0) {value []})
children))
zipper))
(def: #export (append-child value zipper)
(All [a] (-> a (Zipper a) (Zipper a)))
(update@ [#node #tree;children]
(lambda [children]
(List/append children
(list (tree;tree ($ +0) {value []}))))
zipper))
(def: #export (remove zipper)
(All [a] (-> (Zipper a) (Maybe (Zipper a))))
(case (get@ #lefts zipper)
#;Nil
(case (get@ #parent zipper)
#;None
#;None
(#;Some next)
(#;Some (|> next
(update@ [#node #tree;children] (|>. list;tail (default (list)))))))
(#;Cons next side)
(#;Some (|> zipper
(set@ #lefts side)
(set@ #node next)))))
(do-template [<name> <side>]
[(def: #export (<name> value zipper)
(All [a] (-> a (Zipper a) (Maybe (Zipper a))))
(case (get@ #parent zipper)
#;None
#;None
_
(#;Some (|> zipper
(update@ <side> (lambda [side]
(#;Cons (tree;tree ($ +0) {value []})
side)))))))]
[insert-left #lefts]
[insert-right #rights]
)
(do-template [<name> <h-side> <h-op> <v-op>]
[(def: #export (<name> zipper)
(All [a] (-> (Zipper a) (Zipper a)))
(case (get@ <h-side> zipper)
#;Nil
(<v-op> zipper)
_
(<h-op> zipper)))]
[next #rights right down]
[prev #lefts left up]
)
(def: #export (end? zipper)
(All [a] (-> (Zipper a) Bool))
(and (list;empty? (get@ #rights zipper))
(list;empty? (children zipper))))
(def: #export (root? zipper)
(All [a] (-> (Zipper a) Bool))
(case (get@ #parent zipper)
#;None
true
_
false))
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