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lists.pl -- SICStus 4-compatible library(lists). |
The following predicates are exported from this file while their implementation is defined in imported modules or non-module files loaded by this module.
call(Goal, Xi)
succeeds.
call(Goal, Xi)
fails.
call(Pred, Xi, Place)
,
where Place must be unified to one of <
, =
or >
.
Pred must be deterministic.
maplist(G, [X_11, ..., X_1n], [X_21, ..., X_2n], ..., [X_m1, ..., X_mn]) :- call(G, X_11, ..., X_m1), call(G, X_12, ..., X_m2), ... call(G, X_1n, ..., X_mn).
This family of predicates is deterministic iff Goal is deterministic
and List1 is a proper list, i.e., a list that ends in []
.
maplist(G, [X_11, ..., X_1n], [X_21, ..., X_2n], ..., [X_m1, ..., X_mn]) :- call(G, X_11, ..., X_m1), call(G, X_12, ..., X_m2), ... call(G, X_1n, ..., X_mn).
This family of predicates is deterministic iff Goal is deterministic
and List1 is a proper list, i.e., a list that ends in []
.
maplist(G, [X_11, ..., X_1n], [X_21, ..., X_2n], ..., [X_m1, ..., X_mn]) :- call(G, X_11, ..., X_m1), call(G, X_12, ..., X_m2), ... call(G, X_1n, ..., X_mn).
This family of predicates is deterministic iff Goal is deterministic
and List1 is a proper list, i.e., a list that ends in []
.
call(Goal, ElemIn, _)
fails are omitted from ListOut. For example (using library(yall)):
?- convlist([X,Y]>>(integer(X), Y is X^2), [3, 5, foo, 2], L). L = [9, 25, 4].
?- transpose([[1,2,3],[4,5,6],[7,8,9]], Ts). Ts = [[1, 4, 7], [2, 5, 8], [3, 6, 9]].
This predicate is useful in many constraint programs. Consider for instance Sudoku:
sudoku(Rows) :- length(Rows, 9), maplist(same_length(Rows), Rows), append(Rows, Vs), Vs ins 1..9, maplist(all_distinct, Rows), transpose(Rows, Columns), maplist(all_distinct, Columns), Rows = [As,Bs,Cs,Ds,Es,Fs,Gs,Hs,Is], blocks(As, Bs, Cs), blocks(Ds, Es, Fs), blocks(Gs, Hs, Is). blocks([], [], []). blocks([N1,N2,N3|Ns1], [N4,N5,N6|Ns2], [N7,N8,N9|Ns3]) :- all_distinct([N1,N2,N3,N4,N5,N6,N7,N8,N9]), blocks(Ns1, Ns2, Ns3). problem(1, [[_,_,_,_,_,_,_,_,_], [_,_,_,_,_,3,_,8,5], [_,_,1,_,2,_,_,_,_], [_,_,_,5,_,7,_,_,_], [_,_,4,_,_,_,1,_,_], [_,9,_,_,_,_,_,_,_], [5,_,_,_,_,_,_,7,3], [_,_,2,_,1,_,_,_,_], [_,_,_,_,4,_,_,_,9]]).
Sample query:
?- problem(1, Rows), sudoku(Rows), maplist(portray_clause, Rows). [9, 8, 7, 6, 5, 4, 3, 2, 1]. [2, 4, 6, 1, 7, 3, 9, 8, 5]. [3, 5, 1, 9, 2, 8, 7, 4, 6]. [1, 2, 8, 5, 3, 7, 6, 9, 4]. [6, 3, 4, 8, 9, 2, 1, 5, 7]. [7, 9, 5, 4, 6, 1, 8, 3, 2]. [5, 1, 9, 2, 8, 6, 4, 7, 3]. [4, 7, 2, 3, 1, 9, 5, 6, 8]. [8, 6, 3, 7, 4, 5, 2, 1, 9]. Rows = [[9, 8, 7, 6, 5, 4, 3, 2|...], ... , [...|...]].
?- select(b, [a,b,c,b], 2, X). X = [a, 2, c, b] ; X = [a, b, c, 2] ; false.
\+ Elem \=
H
, which implies that Elem is not changed.
?- nth0(I, [a,b,c], E, R). I = 0, E = a, R = [b, c] ; I = 1, E = b, R = [a, c] ; I = 2, E = c, R = [a, b] ; false.
?- nth0(1, L, a1, [a,b]). L = [a, a1, b].
semidet
if List is a list and multi
if List is
a partial list.
proper_length(List, Length) :- is_list(List), length(List, Length).
If both Xs and Ys are provided and both lists have equal length
the order is |Xs|^2. Simply testing whether Xs is a permutation
of Ys can be achieved in order log(|Xs|) using msort/2 as
illustrated below with the semidet
predicate is_permutation/2:
is_permutation(Xs, Ys) :- msort(Xs, Sorted), msort(Ys, Sorted).
The example below illustrates that Xs and Ys being proper lists is not a sufficient condition to use the above replacement.
?- permutation([1,2], [X,Y]). X = 1, Y = 2 ; X = 2, Y = 1 ; false.
Item-Count
pairs that represents the run
length encoding of Items. For example:
?- clumped([a,a,b,a,a,a,a,c,c,c], R). R = [a-2, b-1, a-4, c-3].
?- max_member(@=<, X, [6,1,8,4]). X = 8.
?- min_member(@=<, X, [6,1,8,4]). X = 1.
The following predicates are exported, but not or incorrectly documented.