View source with raw comments or as raw

    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)  2015, VU University Amsterdam
    7    All rights reserved.
    8
    9    Redistribution and use in source and binary forms, with or without
   10    modification, are permitted provided that the following conditions
   11    are met:
   12
   13    1. Redistributions of source code must retain the above copyright
   14       notice, this list of conditions and the following disclaimer.
   15
   16    2. Redistributions in binary form must reproduce the above copyright
   17       notice, this list of conditions and the following disclaimer in
   18       the documentation and/or other materials provided with the
   19       distribution.
   20
   21    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   22    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   23    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   24    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   25    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   26    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   27    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   28    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   29    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   31    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   32    POSSIBILITY OF SUCH DAMAGE.
   33*/
   34
   35:- module(dicts,
   36          [ dicts_same_tag/2,           % +List, -Tag
   37            dict_size/2,                % +Dict, -KeyCount
   38            dict_keys/2,                % +Dict, -Keys
   39            dicts_same_keys/2,          % +DictList, -Keys
   40            dicts_to_same_keys/3,       % +DictsIn, :OnEmpty, -DictsOut
   41            dict_fill/4,                % +Value, +Key, +Dict, -Value
   42            dict_no_fill/3,             % +Key, +Dict, -Value
   43            dicts_join/3,               % +Key, +DictsIn, -Dicts
   44            dicts_join/4,               % +Key, +Dicts1, +Dicts2, -Dicts
   45            dicts_slice/3,              % +Keys, +DictsIn, -DictsOut
   46            dicts_to_compounds/4        % ?Dicts, +Keys, :OnEmpty, ?Compounds
   47          ]).   48:- autoload(library(apply),[maplist/2,maplist/3]).   49:- autoload(library(lists),[append/2,append/3]).   50:- autoload(library(ordsets),[ord_subtract/3]).   51:- autoload(library(pairs),[pairs_keys/2,pairs_keys_values/3]).   52
   53
   54:- meta_predicate
   55    dicts_to_same_keys(+,3,-),
   56    dicts_to_compounds(?,+,3,?).

Dict utilities

This library defines utilities that operate on lists of dicts, notably to make lists of dicts consistent by adding missing keys, converting between lists of compounds and lists of dicts, joining and slicing lists of dicts. */

dicts_same_tag(+List, -Tag) is semidet: True when List is a list of dicts that all have the tag Tag.

   70dicts_same_tag(List, Tag) :-
   71    maplist(keys_tag(Tag), List).
   72
   73keys_tag(Tag, Dict) :-
   74    is_dict(Dict, Tag).

dict_size(+Dict, -KeyCount) is det: True when KeyCount is the number of keys in Dict.

   80dict_size(Dict, KeyCount) :-
   81    must_be(dict,Dict),
   82    compound_name_arity(Dict,_,Arity),
   83    KeyCount is (Arity-1)//2.

dict_keys(+Dict, -Keys) is det: True when Keys is an ordered set of the keys appearing in Dict.

   89dict_keys(Dict, Keys) :-
   90    dict_pairs(Dict, _Tag, Pairs),
   91    pairs_keys(Pairs, Keys).

dicts_same_keys(+List, -Keys) is semidet: True if List is a list of dicts that all have the same keys and Keys is an ordered set of these keys.

   99dicts_same_keys(List, Keys) :-
  100    maplist(keys_dict(Keys), List).
  101
  102keys_dict(Keys, Dict) :-
  103    dict_keys(Dict, Keys).

dicts_to_same_keys(+DictsIn, :OnEmpty, -DictsOut)

DictsOut is a copy of DictsIn, where each dict contains all keys appearing in all dicts of DictsIn. Values for keys that are added to a dict are produced by calling OnEmpty as below. The predicate dict_fill/4 provides an implementation that fills all new cells with a predefined value.

call(:OnEmpty, +Key, +Dict, -Value)

  117dicts_to_same_keys(Dicts, _, Table) :-
  118    dicts_same_keys(Dicts, _),
  119    !,
  120    Table = Dicts.
  121dicts_to_same_keys(Dicts, OnEmpty, Table) :-
  122    maplist(dict_keys, Dicts, KeysList),
  123    append(KeysList, Keys0),
  124    sort(Keys0, Keys),
  125    maplist(extend_dict(Keys, OnEmpty), Dicts, Table).
  126
  127extend_dict(Keys, OnEmpty, Dict0, Dict) :-
  128    dict_pairs(Dict0, Tag, Pairs),
  129    pairs_keys(Pairs, DictKeys),
  130    ord_subtract(Keys, DictKeys, Missing),
  131    (   Missing == []
  132    ->  Dict = Dict0
  133    ;   maplist(key_value_pair(Dict0, OnEmpty), Missing, NewPairs),
  134        append(NewPairs, Pairs, AllPairs),
  135        dict_pairs(Dict, Tag, AllPairs)
  136    ).
  137
  138key_value_pair(Dict, OnEmpty, Key, Key-Value) :-
  139    call(OnEmpty, Key, Dict, Value).

dict_fill(+ValueIn, +Key, +Dict, -Value) is det

Implementation for the dicts_to_same_keys/3 OnEmpty closure that fills new cells with a copy of ValueIn. Note that copy_term/2 does not really copy ground terms. Below are two examples. Note that when filling empty cells with a variable, each empty cell is bound to a new variable.

?- dicts_to_same_keys([r{x:1}, r{y:2}], dict_fill(null), L).
L = [r{x:1, y:null}, r{x:null, y:2}].
?- dicts_to_same_keys([r{x:1}, r{y:2}], dict_fill(_), L).
L = [r{x:1, y:_G2005}, r{x:_G2036, y:2}].

Use dict_no_fill/3 to raise an error if a dict is missing a key.

  158dict_fill(ValueIn, _, _, Value) :-
  159    copy_term(ValueIn, Value).

dict_no_fill is det: Can be used instead of dict_fill/4 to raise an exception if some dict is missing a key.

  166dict_no_fill(Key, Dict, Value) :-
  167    Value = Dict.Key.

dicts_join(+Key, +DictsIn, -Dicts) is semidet

Join dicts in Dicts that have the same value for Key, provided they do not have conflicting values on other keys. For example:

?- dicts_join(x, [r{x:1, y:2}, r{x:1, z:3}, r{x:2,y:4}], L).
L = [r{x:1, y:2, z:3}, r{x:2, y:4}].

Errors: - existence_error(key, Key, Dict) if a dict in Dicts1 or Dicts2 does not contain Key.

  182dicts_join(Join, Dicts0, Dicts) :-
  183    sort(Join, @=<, Dicts0, Dicts1),
  184    join(Dicts1, Join, Dicts).
  185
  186join([], _, []) :- !.
  187join([H0|T0], Key, [H|T]) :-
  188    !,
  189    get_dict(Key, H0, V0),
  190    join_same(T0, Key, V0, H0, H, T1),
  191    join(T1, Key, T).
  192join([One], _, [One]) :- !.
  193
  194join_same([H|T0], Key, V0, D0, D, T) :-
  195    get_dict(Key, H, V),
  196    V == V0,
  197    !,
  198    D0 >:< H,
  199    put_dict(H, D0, D1),
  200    join_same(T0, Key, V0, D1, D, T).
  201join_same(DL, _, _, D, D, DL).

dicts_join(+Key, +Dicts1, +Dicts2, -Dicts) is semidet

Join two lists of dicts (Dicts1 and Dicts2) on Key. Each pair D1-D2 from Dicts1 and Dicts2 that have the same (==) value for Key creates a new dict D with the union of the keys from D1 and D2, provided D1 and D2 to not have conflicting values for some key. For example:

?- DL1 = [r{x:1,y:1},r{x:2,y:4}],
   DL2 = [r{x:1,z:2},r{x:3,z:4}],
   dicts_join(x, DL1, DL2, DL).
   DL = [r{x:1, y:1, z:2}, r{x:2, y:4}, r{x:3, z:4}].

Errors: - existence_error(key, Key, Dict) if a dict in Dicts1 or Dicts2 does not contain Key.

  221dicts_join(Join, Dicts1, Dicts2, Dicts) :-
  222    sort(Join, @=<, Dicts1, Dicts11),
  223    sort(Join, @=<, Dicts2, Dicts21),
  224    join(Dicts11, Dicts21, Join, Dicts).
  225
  226join([], [], _, []) :- !.
  227join([D1|T1], [D2|T2], Join, [DNew|MoreDicts]) :-
  228    !,
  229    get_dict(Join, D1, K1),
  230    get_dict(Join, D2, K2),
  231    compare(Diff, K1, K2),
  232    (   Diff == (=)
  233    ->  D1 >:< D2,
  234        put_dict(D1, D2, DNew),
  235        join(T1, T2, Join, MoreDicts)
  236    ;   Diff == (<)
  237    ->  DNew = D1,
  238        join(T1, [D2|T2], Join, MoreDicts)
  239    ;   DNew = D2,
  240        join([D1|T1], T2, Join, MoreDicts)
  241    ).
  242join([], Dicts, _, Dicts) :- !.
  243join(Dicts, [], _, Dicts).

dicts_slice(+Keys, +DictsIn, -DictsOut) is det: DictsOut is a list of Dicts only containing values for Keys.

  250dicts_slice(Keys, DictsIn, DictsOut) :-
  251    sort(Keys, SortedKeys),
  252    maplist(dict_slice(SortedKeys), DictsIn, DictsOut).
  253
  254dict_slice(Keys, DictIn, DictOut) :-
  255    dict_pairs(DictIn, Tag, PairsIn),
  256    slice_pairs(Keys, PairsIn, PairsOut),
  257    dict_pairs(DictOut, Tag, PairsOut).
  258
  259slice_pairs([], _, []) :- !.
  260slice_pairs(_, [], []) :- !.
  261slice_pairs([H|T0], [P|PL], Pairs) :-
  262    P = K-_,
  263    compare(D, H, K),
  264    (   D == (=)
  265    ->  Pairs = [P|More],
  266        slice_pairs(T0, PL, More)
  267    ;   D == (<)
  268    ->  slice_pairs(T0, [P|PL], Pairs)
  269    ;   slice_pairs([H|T0], PL, Pairs)
  270    ).

dicts_to_compounds(?Dicts, +Keys, :OnEmpty, ?Compounds) is semidet

True when Dicts and Compounds are lists of the same length and each element of Compounds is a compound term whose arguments represent the values associated with the corresponding keys in Keys. When converting from dict to row, OnEmpty is used to compute missing values. The functor for the compound is the same as the tag of the pair. When converting from dict to row and the dict has no tag, the functor row is used. For example:

?- Dicts = [_{x:1}, _{x:2, y:3}],
   dicts_to_compounds(Dicts, [x], dict_fill(null), Compounds).
Compounds = [row(1), row(2)].
?- Dicts = [_{x:1}, _{x:2, y:3}],
   dicts_to_compounds(Dicts, [x,y], dict_fill(null), Compounds).
Compounds = [row(1, null), row(2, 3)].
?- Compounds = [point(1,1), point(2,4)],
   dicts_to_compounds(Dicts, [x,y], dict_fill(null), Compounds).
Dicts = [point{x:1, y:1}, point{x:2, y:4}].

When converting from Dicts to Compounds Keys may be computed by dicts_same_keys/2.

  297dicts_to_compounds(Dicts, Keys, OnEmpty, Compounds) :-
  298    maplist(dict_to_compound(Keys, OnEmpty), Dicts, Compounds).
  299
  300dict_to_compound(Keys, OnEmpty, Dict, Row) :-
  301    is_dict(Dict, Tag),
  302    !,
  303    default_tag(Tag, row),
  304    maplist(key_value(Dict, OnEmpty), Keys, Values),
  305    compound_name_arguments(Row, Tag, Values).
  306dict_to_compound(Keys, _, Dict, Row) :-
  307    compound(Row),
  308    compound_name_arguments(Row, Tag, Values),
  309    pairs_keys_values(Pairs, Keys, Values),
  310    dict_pairs(Dict, Tag, Pairs).
  311
  312default_tag(Tag, Tag) :- !.
  313default_tag(_, _).
  314
  315key_value(Dict, OnEmpty, Key, Value) :-
  316    (   get_dict(Key, Dict, Value0)
  317    ->  Value = Value0
  318    ;   call(OnEmpty, Key, Dict, Value)
  319    )