SWI-Prolog で JSON ファイルを読む

json_read.pl

/* ------------------------------------------------------------------- */
/*
    json_read.pl

                        Oct/18/2018
*/
/* ------------------------------------------------------------------- */
:- use_module([ library(http/json) ]).
:- initialization main.

/* ------------------------------------------------------------------- */
%% [4-6-8]:
display_line_proc(Dict,Key) :-
    write(current_output ,Key),
    write(current_output ,'\t'),
    write(current_output ,Dict.Key.name),
    write(current_output ,'\t'),
    write(current_output ,Dict.Key.population),
    write(current_output ,'\t'),
    writeln(current_output ,Dict.Key.date_mod).
/* ------------------------------------------------------------------- */
%% [4-6]:
print_list(Dict,[]).
print_list(Dict,[Element|List]) :-
    display_line_proc(Dict,Element),
    print_list(Dict,List).

/* ------------------------------------------------------------------- */
%% [4]:
reading_JSON_term(File_in) :-
    write(File_in),nl,
    open(File_in, read, Stream, [] ),
    json_read_dict(Stream, Dict, []),
    close(Stream),
%%
    dict_keys(Dict,Keys),
    length(Keys,Ll),
    writeln(current_output , Ll),
    print_list(Dict,Keys).

/* ------------------------------------------------------------------- */
main(Argv) :-
    format('*** 開始 ***\n'),
    format('Argv: ~w\n', [Argv]),
    [File_in|_] = Argv,
    reading_JSON_term(File_in),
    format('*** 終了 ***\n'),
    halt.

/* ------------------------------------------------------------------- */

実行方法

swipl -f ./json_read.pl /var/tmp/json/cities.json