1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2007-2023, University of Amsterdam
    7                              VU University Amsterdam
    8                              SWI-Prolog Solutions b.v.
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in
   20       the documentation and/or other materials provided with the
   21       distribution.
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   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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   35*/
   36
   37:- module(apply,
   38          [ include/3,                  % :Pred, +List, -Ok
   39            exclude/3,                  % :Pred. +List, -NotOk
   40            partition/4,                % :Pred, +List, -Included, -Excluded
   41            partition/5,                % :Pred, +List, ?Less, ?Equal, ?Greater
   42            maplist/2,                  % :Pred, +List
   43            maplist/3,                  % :Pred, ?List, ?List
   44            maplist/4,                  % :Pred, ?List, ?List, ?List
   45            maplist/5,                  % :Pred, ?List, ?List, ?List, ?List
   46            convlist/3,                 % :Pred, +List, -List
   47            foldl/4,                    % :Pred, +List, ?V0, ?V
   48            foldl/5,                    % :Pred, +List1, +List2, ?V0, ?V
   49            foldl/6,                    % :Pred, +List1, +List2, +List3, ?V0, ?V
   50            foldl/7,                    % :Pred, +List1, +List2, +List3, +List4,
   51                                        % ?V0, ?V
   52            scanl/4,                    % :Pred, +List, ?V0, ?Vs
   53            scanl/5,                    % :Pred, +List1, +List2, ?V0, ?Vs
   54            scanl/6,                    % :Pred, +List1, +List2, +List3, ?V0, ?Vs
   55            scanl/7                     % :Pred, +List1, +List2, +List3, +List4,
   56                                        % ?V0, ?Vs
   57          ]).   58:- autoload(library(error),[must_be/2]).   59:- set_prolog_flag(generate_debug_info, false).

?- maplist(=, [foo, foo], [X, Y]).
?- maplist(=(foo), [X, Y]).

   81:- meta_predicate
   82    include(1, +, -),
   83    exclude(1, +, -),
   84    partition(1, +, -, -),
   85    partition(2, +, -, -, -),
   86    maplist(1, ?),
   87    maplist(2, ?, ?),
   88    maplist(3, ?, ?, ?),
   89    maplist(4, ?, ?, ?, ?),
   90    convlist(2, +, -),
   91    foldl(3, +, +, -),
   92    foldl(4, +, +, +, -),
   93    foldl(5, +, +, +, +, -),
   94    foldl(6, +, +, +, +, +, -),
   95    scanl(3, +, +, -),
   96    scanl(4, +, +, +, -),
   97    scanl(5, +, +, +, +, -),
   98    scanl(6, +, +, +, +, +, -).

 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.

  110include(Goal, List, Included) :-
  111    include_(List, Goal, Included).
  112
  113include_([], _, []).
  114include_([X1|Xs1], P, Included) :-
  115    (   call(P, X1)
  116    ->  Included = [X1|Included1]
  117    ;   Included = Included1
  118    ),
  119    include_(Xs1, P, Included1).

 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

  129exclude(Goal, List, Included) :-
  130    exclude_(List, Goal, Included).
  131
  132exclude_([], _, []).
  133exclude_([X1|Xs1], P, Included) :-
  134    (   call(P, X1)
  135    ->  Included = Included1
  136    ;   Included = [X1|Included1]
  137    ),
  138    exclude_(Xs1, P, Included1).

 partition(:Pred, +List, ?Included, ?Excluded) is det

Filter elements of List according to Pred. True if Included contains all elements for which call(Pred, X) succeeds and Excluded contains the remaining elements.

See also

- include/3, exclude/3, partition/5.

  149partition(Pred, List, Included, Excluded) :-
  150    partition_(List, Pred, Included, Excluded).
  151
  152partition_([], _, [], []).
  153partition_([H|T], Pred, Incl, Excl) :-
  154    (   call(Pred, H)
  155    ->  Incl = [H|I],
  156        partition_(T, Pred, I, Excl)
  157    ;   Excl = [H|E],
  158        partition_(T, Pred, Incl, E)
  159    ).

 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

  171partition(Pred, List, Less, Equal, Greater) :-
  172    partition_(List, Pred, Less, Equal, Greater).
  173
  174partition_([], _, [], [], []).
  175partition_([H|T], Pred, L, E, G) :-
  176    call(Pred, H, Diff),
  177    partition_(Diff, H, Pred, T, L, E, G).
  178
  179partition_(<, H, Pred, T, L, E, G) :-
  180    !,
  181    L = [H|Rest],
  182    partition_(T, Pred, Rest, E, G).
  183partition_(=, H, Pred, T, L, E, G) :-
  184    !,
  185    E = [H|Rest],
  186    partition_(T, Pred, L, Rest, G).
  187partition_(>, H, Pred, T, L, E, G) :-
  188    !,
  189    G = [H|Rest],
  190    partition_(T, Pred, L, E, Rest).
  191partition_(Diff, _, _, _, _, _, _) :-
  192    must_be(oneof([<,=,>]), Diff).
  193
  194
  195                 /*******************************
  196                 *            MAPLIST           *
  197                 *******************************/

 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 [].

  221maplist(Goal, List) :-
  222    maplist_(List, Goal).
  223
  224maplist_([], _).
  225maplist_([Elem|Tail], Goal) :-
  226    call(Goal, Elem),
  227    maplist_(Tail, Goal).
  228
  229maplist(Goal, List1, List2) :-
  230    maplist_(List1, List2, Goal).
  231
  232maplist_([], [], _).
  233maplist_([Elem1|Tail1], [Elem2|Tail2], Goal) :-
  234    call(Goal, Elem1, Elem2),
  235    maplist_(Tail1, Tail2, Goal).
  236
  237maplist(Goal, List1, List2, List3) :-
  238    maplist_(List1, List2, List3, Goal).
  239
  240maplist_([], [], [], _).
  241maplist_([Elem1|Tail1], [Elem2|Tail2], [Elem3|Tail3], Goal) :-
  242    call(Goal, Elem1, Elem2, Elem3),
  243    maplist_(Tail1, Tail2, Tail3, Goal).
  244
  245maplist(Goal, List1, List2, List3, List4) :-
  246    maplist_(List1, List2, List3, List4, Goal).
  247
  248maplist_([], [], [], [], _).
  249maplist_([Elem1|Tail1], [Elem2|Tail2], [Elem3|Tail3], [Elem4|Tail4], Goal) :-
  250    call(Goal, Elem1, Elem2, Elem3, Elem4),
  251    maplist_(Tail1, Tail2, Tail3, Tail4, Goal).

 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).

  268convlist(Goal, ListIn, ListOut) :-
  269    convlist_(ListIn, ListOut, Goal).
  270
  271convlist_([], [], _).
  272convlist_([H0|T0], ListOut, Goal) :-
  273    (   call(Goal, H0, H)
  274    ->  ListOut = [H|T],
  275        convlist_(T0, T, Goal)
  276    ;   convlist_(T0, ListOut, Goal)
  277    ).
  278
  279
  280                 /*******************************
  281                 *            FOLDL             *
  282                 *******************************/

 foldl(:Goal, +List, +V0, -V)

 foldl(:Goal, +List1, +List2, +V0, -V)

 foldl(:Goal, +List1, +List2, +List3, +V0, -V)

 foldl(:Goal, +List1, +List2, +List3, +List4, +V0, -V)

Fold an ensemble of m (0 <= m <= 4) lists of length n head-to-tail ("fold-left"), using columns of m list elements as arguments for Goal. The foldl family of predicates is defined as follows, with V0 an initial value and V the final value of the folding operation:

foldl(G, [X_11, ..., X_1n],
         [X_21, ..., X_2n],
         ...,
         [X_m1, ..., X_mn], V0, V) :-
   call(G, X_11, ..., X_m1, V0, V1),
   call(G, X_12, ..., X_m2, V1, V2),
   ...
   call(G, X_1n, ..., X_mn, V<n-1>, V).

No implementation for a corresponding foldr is given. A foldr implementation would consist in first calling reverse/2 on each of the m input lists, then applying the appropriate foldl. This is actually more efficient than using a properly programmed-out recursive algorithm that cannot be tail-call optimized.

  312foldl(Goal, List, V0, V) :-
  313    foldl_(List, Goal, V0, V).
  314
  315foldl_([], _, V, V).
  316foldl_([H|T], Goal, V0, V) :-
  317    call(Goal, H, V0, V1),
  318    foldl_(T, Goal, V1, V).
  319
  320
  321foldl(Goal, List1, List2, V0, V) :-
  322    foldl_(List1, List2, Goal, V0, V).
  323
  324foldl_([], [], _, V, V).
  325foldl_([H1|T1], [H2|T2], Goal, V0, V) :-
  326    call(Goal, H1, H2, V0, V1),
  327    foldl_(T1, T2, Goal, V1, V).
  328
  329
  330foldl(Goal, List1, List2, List3, V0, V) :-
  331    foldl_(List1, List2, List3, Goal, V0, V).
  332
  333foldl_([], [], [], _, V, V).
  334foldl_([H1|T1], [H2|T2], [H3|T3], Goal, V0, V) :-
  335    call(Goal, H1, H2, H3, V0, V1),
  336    foldl_(T1, T2, T3, Goal, V1, V).
  337
  338
  339foldl(Goal, List1, List2, List3, List4, V0, V) :-
  340    foldl_(List1, List2, List3, List4, Goal, V0, V).
  341
  342foldl_([], [], [], [], _, V, V).
  343foldl_([H1|T1], [H2|T2], [H3|T3], [H4|T4], Goal, V0, V) :-
  344    call(Goal, H1, H2, H3, H4, V0, V1),
  345    foldl_(T1, T2, T3, T4, Goal, V1, V).
  346
  347
  348                 /*******************************
  349                 *             SCANL            *
  350                 *******************************/

 scanl(:Goal, +List, +V0, -Values)

 scanl(:Goal, +List1, +List2, +V0, -Values)

 scanl(:Goal, +List1, +List2, +List3, +V0, -Values)

 scanl(:Goal, +List1, +List2, +List3, +List4, +V0, -Values)

Scan an ensemble of m (0 <= m <= 4) lists of length n head-to-tail ("scan-left"), using columns of m list elements as arguments for Goal. The scanl family of predicates is defined as follows, with V0 an initial value and V the final value of the scanning operation:

scanl(G, [X_11, ..., X_1n],
         [X_21, ..., X_2n],
         ...,
         [X_m1, ..., X_mn], V0, [V0, V1, ..., Vn] ) :-
   call(G, X_11, ..., X_m1, V0, V1),
   call(G, X_12, ..., X_m2, V1, V2),
   ...
   call(G, X_1n, ..., X_mn, V<n-1>, Vn).

scanl behaves like a foldl that collects the sequence of values taken on by the Vx accumulator into a list.

  377scanl(Goal, List, V0, [V0|Values]) :-
  378    scanl_(List, Goal, V0, Values).
  379
  380scanl_([], _, _, []).
  381scanl_([H|T], Goal, V, [VH|VT]) :-
  382    call(Goal, H, V, VH),
  383    scanl_(T, Goal, VH, VT).
  384
  385
  386scanl(Goal, List1, List2, V0, [V0|Values]) :-
  387    scanl_(List1, List2, Goal, V0, Values).
  388
  389scanl_([], [], _, _, []).
  390scanl_([H1|T1], [H2|T2], Goal, V, [VH|VT]) :-
  391    call(Goal, H1, H2, V, VH),
  392    scanl_(T1, T2, Goal, VH, VT).
  393
  394
  395scanl(Goal, List1, List2, List3, V0, [V0|Values]) :-
  396    scanl_(List1, List2, List3, Goal, V0, Values).
  397
  398scanl_([], [], [], _, _, []).
  399scanl_([H1|T1], [H2|T2], [H3|T3], Goal, V, [VH|VT]) :-
  400    call(Goal, H1, H2, H3, V, VH),
  401    scanl_(T1, T2, T3, Goal, VH, VT).
  402
  403
  404scanl(Goal, List1, List2, List3, List4, V0, [V0|Values]) :-
  405    scanl_(List1, List2, List3, List4, Goal, V0, Values).
  406
  407scanl_([], [], [], [], _, _, []).
  408scanl_([H1|T1], [H2|T2], [H3|T3], [H4|T4], Goal, V, [VH|VT]) :-
  409    call(Goal, H1, H2, H3, H4, V, VH),
  410    scanl_(T1, T2, T3, T4, Goal, VH, VT).
  411
  412
  413                 /*******************************
  414                 *            SANDBOX           *
  415                 *******************************/
  416
  417:- multifile
  418    sandbox:safe_meta_predicate/1.  419
  420safe_api(Name/Arity, sandbox:safe_meta_predicate(apply:Name/Arity)).
  421
  422term_expansion(safe_api, Clauses) :-
  423    module_property(apply, exports(API)),
  424    maplist(safe_api, API, Clauses).
  425
  426safe_api