lists.pl -- SICStus 4-compatible library(lists).

To be done

- This library is incomplete. As of SICStus 4.6.0, the following predicates are missing:

append/5
correspond/4
delete/4
one_longer/2
perm/2
perm2/4
rotate_list/[2,3]
segment/2
proper_segment/2
cumlist/[4,5,6]
map_product/4
some/[2,3,4]
somechk/[2,3,4]
exclude/[4,5]
include/[4,5]
group/[3,4,5]
ordered/[1,2]
select_min/[3,4]
select_max/[3,4]
increasing_prefix/[3,4]
decreasing_prefix/[3,4]
clumps/2
keyclumps/2
keyclumped/2

rev(+List, ?Reversed) is semidet

Same as reverse/2, but List must be a proper list.

shorter_list(?Short, ?Long) is nondet

True if Short is a shorter list than Long. The lists' contents are insignificant, only the lengths matter. Mode -Short, +Long can be used to enumerate list skeletons shorter than Long.

prefix(?List, ?Prefix) is nondet

True if Prefix is a prefix of List. Not the same as prefix/2 in SICStus 3 or SWI - the arguments are reversed!

proper_prefix(?List, ?Prefix) is nondet

True if Prefix is a prefix of List, but is not List itself.

suffix(?List, ?Prefix) is nondet

True if Suffix is a suffix of List. Not the same as suffix/2 in SICStus 3 - the arguments are reversed!

proper_suffix(?List, ?Prefix) is nondet

True if Suffix is a suffix of List, but is not List itself.

scanlist(:Pred, ?Xs, ?V1, ?V) is nondet

scanlist(:Pred, ?Xs, ?Ys, ?V1, ?V) is nondet

scanlist(:Pred, ?Xs, ?Ys, ?Zs, ?V1, ?V) is nondet

Same as foldl/[4,5,6].

Compatibility: - SICStus 4

Re-exported predicates

The following predicates are exported from this file while their implementation is defined in imported modules or non-module files loaded by this module.

include(:Goal, +List1, ?List2) is det

Filter elements for which Goal succeeds. True if List2 contains those elements Xi of List1 for which call(Goal, Xi) succeeds.

See also: - exclude/3, partition/4, convlist/3.
Compatibility: - Older versions of SWI-Prolog had sublist/3 with the same arguments and semantics.

exclude(:Goal, +List1, ?List2) is det

Filter elements for which Goal fails. True if List2 contains those elements Xi of List1 for which call(Goal, Xi) fails.

See also: - include/3, partition/4

partition(:Pred, +List, ?Less, ?Equal, ?Greater) is semidet

Filter List according to Pred in three sets. For each element Xi of List, its destination is determined by call(Pred, Xi, Place), where Place must be unified to one of <, = or >. Pred must be deterministic.

See also: - partition/4

maplist(:Goal, ?List1)

maplist(:Goal, ?List1, ?List2)

maplist(:Goal, ?List1, ?List2, ?List3)

maplist(:Goal, ?List1, ?List2, ?List3, ?List4)

True if Goal is successfully applied on all matching elements of the list. The maplist family of predicates is defined as:

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(:Goal, ?List1)

maplist(:Goal, ?List1, ?List2)

maplist(:Goal, ?List1, ?List2, ?List3)

maplist(:Goal, ?List1, ?List2, ?List3, ?List4)

True if Goal is successfully applied on all matching elements of the list. The maplist family of predicates is defined as:

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(:Goal, ?List1)

maplist(:Goal, ?List1, ?List2)

maplist(:Goal, ?List1, ?List2, ?List3)

maplist(:Goal, ?List1, ?List2, ?List3, ?List4)

True if Goal is successfully applied on all matching elements of the list. The maplist family of predicates is defined as:

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 [].

convlist(:Goal, +ListIn, -ListOut) is det

Similar to maplist/3, but elements for which 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].

Compatibility: - Also appears in YAP library(maplist) and SICStus library(lists).

transpose(+Matrix, ?Transpose)

Transpose a list of lists of the same length. Example:

?- 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|...], ... , [...|...]].

same_length(?List1, ?List2, ?Length) is nondet