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Refine Micheal's pqueue changes

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library/pqueue.m:
    Refine Micheal's changes where necessary to conform to our style.

NEWS:
    Updated news file.
This commit is contained in:
Paul Bone
2013-11-19 23:22:28 +11:00
parent b203f7e496
commit d17c9f13a6
2 changed files with 41 additions and 21 deletions
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5
NEWS
View File

@@ -27,6 +27,11 @@ Changes to the Mercury standard library:
* We have added the following predicate to the assoc_list module:
foldl2_values/6.
* We have added the following predicates to the pqueue module:
is_empty/1, peek/3, peek_key/2, peek_value/2, det_peek/3 and merge/3.
We have also added the following fuctions to the pqueue module:
det_peek_key/1 and det_peek_value/1.
NEWS for Mercury 13.05.2
------------------------

57
library/pqueue.m
View File

@@ -40,7 +40,7 @@
:- func pqueue.init = pqueue(K, V).
:- pred pqueue.init(pqueue(K, V)::out) is det.
% Test if a priority queue is empty.
% True iff the priority queue is empty.
%
:- pred pqueue.is_empty(pqueue(K, V)::in) is semidet.
@@ -51,7 +51,7 @@
:- pred pqueue.insert(K::in, V::in, pqueue(K, V)::in, pqueue(K, V)::out)
is det.
% Extract the smallest key/value pair from the priority queue without
% Extract the smallest key-value pair from the priority queue without
% removing it. Fails if the priority queue is empty.
%
:- pred pqueue.peek(pqueue(K, V)::in, K::out, V::out) is semidet.
@@ -85,6 +85,7 @@
% Merges all the entries of one priority queue with another, returning
% the merged list.
%
:- func pqueue.merge(pqueue(K, V), pqueue(K, V)) = pqueue(K, V).
:- pred pqueue.merge(pqueue(K, V)::in, pqueue(K, V)::in, pqueue(K, V)::out)
is det.
@@ -149,14 +150,17 @@ pqueue.peek_value(pqueue(_, _, V, _, _), V).
%---------------------------------------------------------------------------%
pqueue.det_peek(PQ, K, V) :-
( pqueue.peek(PQ, J, T) ->
K = J, V = T
( pqueue.peek(PQ, KPrime, VPrime) ->
K = KPrime,
V = VPrime
;
unexpected($file, $pred, "empty priority queue")
).
pqueue.det_peek_key(PQ) = K :- pqueue.det_peek(PQ, K, _).
pqueue.det_peek_value(PQ) = V :- pqueue.det_peek(PQ, _, V).
pqueue.det_peek_key(PQ) = K :-
pqueue.det_peek(PQ, K, _).
pqueue.det_peek_value(PQ) = V :-
pqueue.det_peek(PQ, _, V).
%---------------------------------------------------------------------------%
@@ -187,7 +191,7 @@ pqueue.insert_2(K, V, pqueue(D0, K0, V0, L0, R0), empty,
pqueue.insert_2(K, V, empty, pqueue(D0, K0, V0, L0, R0),
pqueue(0, K, V, empty, empty), pqueue(D0, K0, V0, L0, R0)).
pqueue.insert_2(K, V, pqueue(D0, K0, V0, L0, R0),
pqueue(D1, K1, V1, L1, R1), PQ1, PQ2) :-
pqueue(D1, K1, V1, L1, R1), PQ1, PQ2) :-
( D0 > D1 ->
pqueue.insert(K, V, pqueue(D1, K1, V1, L1, R1), PQ2),
PQ1 = pqueue(D0, K0, V0, L0, R0)
@@ -231,24 +235,35 @@ pqueue.remove_2(pqueue(D0, K0, V0, L0, R0), pqueue(D1, K1, V1, L1, R1), PQ) :-
%---------------------------------------------------------------------------%
pqueue.merge(A, B) = C :-
pqueue.merge(A, B, C).
merge(A, B) = C :-
merge(A, B, C).
pqueue.merge(A, B, C) :-
( pqueue.length(A) =< pqueue.length(B) ->
pqueue.merge2(A, B, C)
;
pqueue.merge2(B, A, C) ).
merge(A, B, C) :-
( length(A) =< length(B) ->
do_merge(A, B, C)
;
do_merge(B, A, C)
).
:- pred pqueue.merge2(pqueue(K, V)::in, pqueue(K, V)::in, pqueue(K, V)::out)
:- pred do_merge(pqueue(K, V)::in, pqueue(K, V)::in, pqueue(K, V)::out)
is det.
pqueue.merge2(empty, B, B).
pqueue.merge2(A@pqueue(_, _, _, _, _), empty, A).
pqueue.merge2(pqueue(_, K, V, L, R), !.PQ@pqueue(_, _, _, _, _), !:PQ) :-
pqueue.merge2(L, !PQ),
pqueue.merge2(R, !PQ),
pqueue.insert(K, V, !PQ).
do_merge(A, B, C) :-
(
A = empty,
C = B
;
A = pqueue(_, K, V, L, R),
(
B = empty,
C = A
;
B = pqueue(_, _, _, _, _),
do_merge(L, B, C0),
do_merge(R, C0, C1),
insert(K, V, C1, C)
)
).
%---------------------------------------------------------------------------%