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https://github.com/Mercury-Language/mercury.git
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d948aecd92
lots of files: Make a start at implementing code generation for complicated unifications. In the HLDS, change complicated_unify/4 to complicated_unify/2 since we didn't need the extra two args after all. peephole.nl: A couple of minor efficiency improvements. queue.nl: Add queue__queue_to_list/2.
121 lines
3.4 KiB
Mathematica
121 lines
3.4 KiB
Mathematica
%--------------------------------------------------------------------------%
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%--------------------------------------------------------------------------%
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% File: queue.nl.
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% Main author: fjh.
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% This file contains a `queue' ADT.
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% This implementation is in terms of a list pair.
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%--------------------------------------------------------------------------%
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:- module queue.
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:- interface.
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:- import_module int.
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:- type queue(T).
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% `queue__init(Queue)' is true iff `Queue' is an empty queue.
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:- pred queue__init(queue(T)).
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:- mode queue__init(out) is det.
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% 'queue_equal(Q1, Q2)' is true iff Q1 and Q2 contain the same
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% elements in the same order.
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:- pred queue__equal(queue(T), queue(T)).
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:- mode queue__equal(in, in) is semidet.
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% `queue__is_empty(Queue)' is true iff `Queue' is an empty queue.
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:- pred queue__is_empty(queue(T)).
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:- mode queue__is_empty(in) is semidet.
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% `queue__is_full(Queue)' is intended to be true iff `Queue'
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% is a queue whose capacity is exhausted. This
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% implementation allows arbitrary-sized queues, so queue__is_full
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% always fails.
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:- pred queue__is_full(queue(T)).
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:- mode queue__is_full(in) is semidet.
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% `queue__put(Queue0, Elem, Queue)' is true iff `Queue' is
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% the queue which results from appending `Elem' onto the end
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% of `Queue0'.
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:- pred queue__put(queue(T), T, queue(T)).
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:- mode queue__put(in, in, out) is det.
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% `queue__first(Queue, Elem)' is true iff `Queue' is a non-empty
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% queue whose first element is `Elem'.
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:- pred queue__first(queue(T), T).
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:- mode queue__first(in, out) is semidet.
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% `queue__get(Queue0, Elem, Queue)' is true iff `Queue0' is
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% a non-empty queue whose first element is `Elem', and `Queue'
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% the queue which results from removing that element from
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% the front of `Queue0'.
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:- pred queue__get(queue(T), T, queue(T)).
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:- mode queue__get(in, out, out) is semidet.
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% `queue__length(Queue, Length)' is true iff `Queue' is a queue
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% containing `Length' elements.
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:- pred queue__length(queue(T), int).
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:- mode queue__length(in, out) is det.
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% `queue__list_to_queue(List, Queue)' is true iff `Queue' is a queue
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% containing the elements of List, with the first element of List at
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% the head of the queue.
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:- pred queue__list_to_queue(list(T), queue(T)).
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:- mode queue__list_to_queue(in, out) is det.
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%--------------------------------------------------------------------------%
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:- implementation.
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:- import_module list, std_util.
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:- type queue(T) == pair(list(T)).
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queue__init([] - []).
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queue__equal(On0 - Off0, On1 - Off1) :-
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list__reverse(On0, On0R),
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list__append(Off0, On0R, Q0),
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list__reverse(On1, On1R),
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list__append(Off1, On1R, Q1),
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Q0 = Q1.
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queue__is_empty([] - []).
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queue__is_full(_) :- fail.
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queue__put(On - Off, Elem, [Elem | On] - Off).
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queue__first(_On - [Elem | _Off], Elem).
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queue__get(On0 - Off0, Elem, On - Off) :-
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queue__get_2(On0, Off0, Elem, On, Off).
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:- pred queue__get_2(list(T), list(T), T, list(T), list(T)).
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:- mode queue__get_2(in, in, out, out, out) is semidet.
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:- queue__get_2(_, X, _, _, _) when X. % NU-Prolog indexing
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queue__get_2(On, [Elem | Off], Elem, On, Off).
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queue__get_2(On, [], Elem, [], Off) :-
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list__reverse(On, [Elem | Off]).
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queue__length(On - Off, Length) :-
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list__length(On, LengthOn),
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list__length(Off, LengthOff),
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Length is LengthOn + LengthOff.
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queue__list_to_queue(List, [] - List).
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%--------------------------------------------------------------------------%
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