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The new array module.
This commit is contained in:
Andrew Bromage
235
library/array.m
235
library/array.m
@@ -6,14 +6,15 @@
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% array.m
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% Main author: conway.
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% Main author: bromage.
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% this file contains a set of predicates for generating an manipulating
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% an array data structure. The implementation uses 2-3 trees to yield
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% O(logN) performance for accesses and updates. Array creation is an
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% O(NlogN) process.
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% arrays are created with any two integer bounds on the indices.
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% an array data structure. It is based on the original module by conway,
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% which used 2-3 trees to store the array. This uses the map module
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% instead, because it's less likely to contain bugs. :-)
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%
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% Arrays will be internal soon anyway, so it doesn't really matter how
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% efficient this code is, as long as it works.
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%-----------------------------------------------------------------------------%
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%-----------------------------------------------------------------------------%
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@@ -66,182 +67,70 @@
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:- implementation.
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:- import_module require.
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:- import_module require, map.
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:- type array(T) ---> empty
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; node(T)
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; two(
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int,
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int,
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array(T),
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array(T)
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)
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; three(
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int,
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int,
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array(T),
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array(T),
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array(T)
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).
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:- type array(T) ---> array(int, int, map(int,T)).
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array__init(Low, High, Init, Array) :-
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Size0 is High - Low,
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Size is Size0 + 1,
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(
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Size = 0
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->
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Array = empty
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%-----------------------------------------------------------------------------%
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array__init(Low, High, Item, array(Low, High, MapOut)) :-
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map__init(MapIn),
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array__init_2(Low, High, Item, MapIn, MapOut).
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:- pred array__init_2(int, int, T, map(int,T), map(int,T)).
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:- mode array__init_2(in, in, in, in, out) is det.
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array__init_2(Low, High, Item, ArrayIn, ArrayOut) :-
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( Low > High ->
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ArrayIn = ArrayOut
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;
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Size = 1
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->
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Array = node(Init)
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;
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Size = 2
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->
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Array = two(Low, High, node(Init), node(Init))
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;
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Size = 3
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->
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Array = three(Low, High, node(Init), node(Init), node(Init))
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;
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Mod2 is Size mod 2,
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Mod2 = 0,
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Mod3 is Size mod 3,
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Mod3 \= 0
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->
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N is Size // 2,
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L2 is Low + N,
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H1 is L2 - 1,
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array__init(Low, H1, Init, A1),
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array__init(L2, High, Init, A2),
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Array = two(Low, High, A1, A2)
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;
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N is Size // 3,
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L2 is Low + N,
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L3 is L2 + N,
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H1 is L2 - 1,
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H2 is L3 - 1,
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array__init(Low, H1, Init, A1),
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array__init(L2, H2, Init, A2),
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array__init(L3, High, Init, A3),
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Array = three(Low, High, A1, A2, A3)
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map__det_insert(ArrayIn, Low, Item, Array1),
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Low1 is Low+1,
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array__init_2(Low1, High, Item, Array1, ArrayOut)
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).
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%-----------------------------------------------------------------------------%
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array__bounds(empty, 1, 0).
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array__bounds(node(_), 0, 0).
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array__bounds(two(Low, High, _, _), Low, High).
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array__bounds(three(Low, High, _, _, _), Low, High).
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array__bounds(array(Low, High, _), Low, High).
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%-----------------------------------------------------------------------------%
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array__lookup(Array, Index, Item) :-
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array__bounds(Array, Low, High),
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(
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Index < Low
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->
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error("Array index below lower bound")
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array__lookup(array(Low, High, Map), Index, Item) :-
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( ( Low =< Index, Index =< High ) ->
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map__lookup(Map, Index, Item)
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;
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Index > High
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->
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error("Array index above upper bound")
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;
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array__search_2(Array, Index, Item)
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).
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:- pred array__search_2(array(T), int, T).
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:- mode array__search_2(in, in, out) is det.
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array__search_2(empty, _, _) :-
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error("Attempt to access element of non-existent array").
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array__search_2(node(Item), _Index, Item).
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array__search_2(two(Low, High, Left, Right), Index, Item) :-
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Size is High - Low,
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Half is Size // 2,
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Mid is Low + Half,
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(
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Index =< Mid
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->
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array__search_2(Left, Index, Item)
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;
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array__search_2(Right, Index, Item)
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).
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array__search_2(three(Low, High, Left, Middle, Right), Index, Item) :-
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Size is High - Low,
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Size1 is Size + 1,
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Third is Size1 // 3,
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Mid1 is Low + Third,
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Mid2 is Mid1 + Third,
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(
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Index < Mid1
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->
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array__search_2(Left, Index, Item)
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;
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Index < Mid2
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->
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array__search_2(Middle, Index, Item)
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;
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array__search_2(Right, Index, Item)
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error("Array subscript out of bounds")
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).
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%-----------------------------------------------------------------------------%
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array__set(empty, _, _, empty) :-
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error("Attempt to access element of non-existent array").
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array__set(node(_), _Index, Item, node(Item)).
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array__set(two(Low, High, Left, Right), Index, Item, A) :-
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Size is High - Low,
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Half is Size // 2,
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Mid is Low + Half,
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(
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Index < Mid
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->
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array__set(Left, Index, Item, Left1),
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A = two(Low, High, Left1, Right)
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array__set(array(Low, High, MapIn), Index, Item, array(Low, High, MapOut)) :-
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( ( Low =< Index, Index =< High ) ->
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map__set(MapIn, Index, Item, MapOut)
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;
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array__set(Right, Index, Item, Right1),
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A = two(Low, High, Left, Right1)
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).
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array__set(three(Low, High, Left, Middle, Right), Index, Item, A) :-
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Size is High - Low,
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Size1 is Size + 1,
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Third is Size1 // 3,
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Mid1 is Low + Third,
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Mid2 is Mid1 + Third,
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(
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Index < Mid1
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->
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array__set(Left, Index, Item, Left1),
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A = three(Low, High, Left1, Middle, Right)
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;
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Index < Mid2
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->
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array__set(Middle, Index, Item, Middle1),
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A = three(Low, High, Left, Middle1, Right)
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;
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array__set(Right, Index, Item, Right1),
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A = three(Low, High, Left, Middle, Right1)
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error("Array subscript out of bounds")
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).
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%-----------------------------------------------------------------------------%
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array__resize(Array0, L, H, Array) :-
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array__bounds(Array0, L0, H0),
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array__lookup(Array0, L0, Item),
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int__max(L, L0, L1),
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int__min(H, H0, H1),
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array__fetch_items(Array0, L1, H1, Items),
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array__init(L, H, Item, Array1),
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array__insert_items(Array1, L1, Items, Array).
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array__bounds(Array0, L0, H0),
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array__lookup(Array0, L0, Item),
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int__max(L, L0, L1),
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int__min(H, H0, H1),
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array__fetch_items(Array0, L1, H1, Items),
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array__init(L, H, Item, Array1),
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array__insert_items(Array1, L1, Items, Array).
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%-----------------------------------------------------------------------------%
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array__from_list([], empty).
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array__from_list([Head | Tail], Array) :-
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list__length(Tail, Len1),
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array__init(0, Len1, Head, Array0),
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array__insert_items(Array0, 1, Tail, Array).
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array__from_list([], array(1, 0, Map)) :-
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map__init(Map).
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array__from_list(List, Array) :-
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List = [ Head | Tail ],
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list__length(List, Len),
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array__init(1, Len, Head, Array0),
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array__insert_items(Array0, 2, Tail, Array).
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%-----------------------------------------------------------------------------%
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@@ -250,15 +139,15 @@ array__from_list([Head | Tail], Array) :-
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array__insert_items(Array, _N, [], Array).
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array__insert_items(Array0, N, [Head|Tail], Array) :-
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array__set(Array0, N, Head, Array1),
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N1 is N + 1,
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array__insert_items(Array1, N1, Tail, Array).
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array__set(Array0, N, Head, Array1),
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N1 is N + 1,
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array__insert_items(Array1, N1, Tail, Array).
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%-----------------------------------------------------------------------------%
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array__to_list(Array, List) :-
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array__bounds(Array, Low, High),
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array__fetch_items(Array, Low, High, List).
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array__bounds(Array, Low, High),
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array__fetch_items(Array, Low, High, List).
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%-----------------------------------------------------------------------------%
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@@ -266,16 +155,16 @@ array__to_list(Array, List) :-
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:- mode array__fetch_items(in, in, in, out) is det.
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array__fetch_items(Array, Low, High, List) :-
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(
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Low > High
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->
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List = []
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;
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Low1 is Low + 1,
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array__fetch_items(Array, Low1, High, List0),
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array__search_2(Array, Low, Item),
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List = [Item|List0]
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).
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(
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Low > High
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->
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List = []
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;
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Low1 is Low + 1,
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array__fetch_items(Array, Low1, High, List0),
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array__lookup(Array, Low, Item),
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List = [Item|List0]
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).
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%-----------------------------------------------------------------------------%
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%-----------------------------------------------------------------------------%
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