Module "maps"

Jan Burse, created Aug 17. 2019
* This module provides unordered maps. The unordered maps are
* represented by lists of key value pairs [k1-v1, .., kn-vn]. The
* lists need not be key ordered or key duplicate free. During
* operations for duplicates the first key wins:
* Examples:
* ?- get([2-a,1-b], 1, X).
* X = b
* ?- put([2-a,1-b], 1, c, X).
* X = [2-a,1-c]
* The realization uses a membership check based on (==)/2. As a
* result the predicates are safe to be used with non-ground terms.
* On the other hand, since this comparison is not arithmetical,
* 1 and 1.0 are for example considered different.
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:- package(library(jekpro/frequent/experiment)).
:- module(maps, []).
* get(M, K, V):
* The predicate succeeds for the value V associated with the
* key K in the map M.
:- public get/3.
get([K-V|_], J, U) :- J == K, !, U = V.
get([_|M], J, U) :- get(M, J, U).
* put(M, K, V, N):
* The predicate succeeds for a map N where the value V is associated
* with the key K and the other key values are associated as in
* the map M.
:- public put/4.
put([K-_|M], J, U, R) :- J == K, !, R = [K-U|M].
put([A|M], J, U, [A|N]) :- put(M, J, U, N).
put([], J, U, [J-U]).
* remove(M, K, N):
* The predicate succeeds for a map N where the key K has no value
* and the other key values are associated as in the map M.
:- public remove/3.
remove([K-_|M], J, R) :- J == K, !, R = M.
remove([A|M], J, [A|N]) :- remove(M, J, N).
remove([], _, []).