/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2003-2016, University of Amsterdam
VU University Amsterdam
All rights reserved.
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modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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*/
:- module(swi_option,
[ option/2, % +Term, +List
option/3, % +Term, +List, +Default
select_option/3, % +Term, +Options, -RestOpts
select_option/4, % +Term, +Options, -RestOpts, +Default
merge_options/3, % +New, +Old, -Merged
meta_options/3, % :IsMeta, :OptionsIn, -OptionsOut
dict_options/2 % ?Dict, ?Options
]).
:- use_module(library(lists)).
:- use_module(library(error)).
:- set_prolog_flag(generate_debug_info, false).
:- meta_predicate
meta_options(1, :, -).
/** <module> Option list processing
The library(option) provides some utilities for processing option lists.
Option lists are commonly used as an alternative for many arguments.
Examples of built-in predicates are open/4 and write_term/3. Naming the
arguments results in more readable code, and the list nature makes it
easy to extend the list of options accepted by a predicate. Option lists
come in two styles, both of which are handled by this library.
$ Name(Value) :
This is the preferred style.
$ Name = Value :
This is often used, but deprecated.
Processing options inside time-critical code (loops) can cause serious
overhead. One possibility is to define a record using library(record)
and initialise this using make_<record>/2. In addition to providing good
performance, this also provides type-checking and central declaration of
defaults.
==
:- record atts(width:integer=100, shape:oneof([box,circle])=box).
process(Data, Options) :-
make_atts(Options, Attributes),
action(Data, Attributes).
action(Data, Attributes) :-
atts_shape(Attributes, Shape),
...
==
Options typically have exactly one argument. The library does support
options with 0 or more than one argument with the following
restrictions:
- The predicate option/3 and select_option/4, involving default are
meaningless. They perform an arg(1, Option, Default), causing
failure without arguments and filling only the first option-argument
otherwise.
- meta_options/3 can only qualify options with exactly one argument.
@tbd We should consider putting many options in an assoc or record
with appropriate preprocessing to achieve better performance.
@see library(record)
@see Option processing capabilities may be declared using the
directive predicate_options/3.
*/
%! option(?Option, +OptionList, +Default) is semidet.
%
% Get an Option from OptionList. OptionList can use the
% Name=Value as well as the Name(Value) convention.
%
% @param Option Term of the form Name(?Value).
option(Opt, Options, Default) :-
is_dict(Options),
!,
functor(Opt, Name, 1),
( get_dict(Name, Options, Val)
-> true
; Val = Default
),
arg(1, Opt, Val).
option(Opt, Options, Default) :- % make option processing stead-fast
functor(Opt, Name, Arity),
functor(GenOpt, Name, Arity),
( get_option(GenOpt, Options)
-> Opt = GenOpt
; arg(1, Opt, Default)
).
%! option(?Option, +OptionList) is semidet.
%
% Get an Option from OptionList. OptionList can use the Name=Value
% as well as the Name(Value) convention. Fails silently if the
% option does not appear in OptionList.
%
% @param Option Term of the form Name(?Value).
option(Opt, Options) :- % make option processing stead-fast
is_dict(Options),
!,
functor(Opt, Name, 1),
get_dict(Name, Options, Val),
arg(1, Opt, Val).
option(Opt, Options) :- % make option processing stead-fast
functor(Opt, Name, Arity),
functor(GenOpt, Name, Arity),
get_option(GenOpt, Options),
!,
Opt = GenOpt.
get_option(Opt, Options) :-
memberchk(Opt, Options),
!.
get_option(Opt, Options) :-
functor(Opt, OptName, 1),
arg(1, Opt, OptVal),
memberchk(OptName=OptVal, Options),
!.
%! select_option(?Option, +Options, -RestOptions) is semidet.
%
% Get and remove Option from an option list. As option/2, removing
% the matching option from Options and unifying the remaining
% options with RestOptions.
select_option(Opt, Options0, Options) :-
is_dict(Options0),
!,
functor(Opt, Name, 1),
get_dict(Name, Options0, Val),
arg(1, Opt, Val),
del_dict(Name, Options0, Val, Options).
select_option(Opt, Options0, Options) :- % stead-fast
functor(Opt, Name, Arity),
functor(GenOpt, Name, Arity),
get_option(GenOpt, Options0, Options),
Opt = GenOpt.
get_option(Opt, Options0, Options) :-
selectchk(Opt, Options0, Options),
!.
get_option(Opt, Options0, Options) :-
functor(Opt, OptName, 1),
arg(1, Opt, OptVal),
selectchk(OptName=OptVal, Options0, Options).
%! select_option(?Option, +Options, -RestOptions, +Default) is det.
%
% Get and remove Option with default value. As select_option/3,
% but if Option is not in Options, its value is unified with
% Default and RestOptions with Options.
select_option(Option, Options, RestOptions, Default) :-
is_dict(Options),
!,
functor(Option, Name, 1),
( get_dict(Name, Options, Val)
-> true
; Val = Default
),
arg(1, Option, Val),
del_dict(Name, Options, _, RestOptions).
select_option(Option, Options, RestOptions, Default) :-
functor(Option, Name, Arity),
functor(GenOpt, Name, Arity),
( get_option(GenOpt, Options, RestOptions)
-> Option = GenOpt
; RestOptions = Options,
arg(1, Option, Default)
).
%! merge_options(+New, +Old, -Merged) is det.
%
% Merge two option lists. Merged is a sorted list of options using
% the canonical format Name(Value) holding all options from New
% and Old, after removing conflicting options from Old.
%
% Multi-values options (e.g., proxy(Host, Port)) are allowed,
% where both option-name and arity define the identity of the
% option.
merge_options([], Old, Merged) :-
!,
canonicalise_options(Old, Merged).
merge_options(New, [], Merged) :-
!,
canonicalise_options(New, Merged).
merge_options(New, Old, Merged) :-
canonicalise_options(New, NCanonical),
canonicalise_options(Old, OCanonical),
sort(NCanonical, NSorted),
sort(OCanonical, OSorted),
ord_merge(NSorted, OSorted, Merged).
ord_merge([], L, L) :- !.
ord_merge(L, [], L) :- !.
ord_merge([NO|TN], [OO|TO], Merged) :-
sort_key(NO, NKey),
sort_key(OO, OKey),
compare(Diff, NKey, OKey),
ord_merge(Diff, NO, NKey, OO, OKey, TN, TO, Merged).
ord_merge(=, NO, _, _, _, TN, TO, [NO|T]) :-
ord_merge(TN, TO, T).
ord_merge(<, NO, _, OO, OKey, TN, TO, [NO|T]) :-
( TN = [H|TN2]
-> sort_key(H, NKey),
compare(Diff, NKey, OKey),
ord_merge(Diff, H, NKey, OO, OKey, TN2, TO, T)
; T = [OO|TO]
).
ord_merge(>, NO, NKey, OO, _, TN, TO, [OO|T]) :-
( TO = [H|TO2]
-> sort_key(H, OKey),
compare(Diff, NKey, OKey),
ord_merge(Diff, NO, NKey, H, OKey, TN, TO2, T)
; T = [NO|TN]
).
sort_key(Option, Name-Arity) :-
functor(Option, Name, Arity).
%! canonicalise_options(+OptionsIn, -OptionsOut) is det.
%
% Rewrite option list from possible Name=Value to Name(Value)
canonicalise_options(Dict, Out) :-
is_dict(Dict),
!,
dict_pairs(Dict, _, Pairs),
canonicalise_options2(Pairs, Out).
canonicalise_options(In, Out) :-
memberchk(_=_, In), % speedup a bit if already ok.
!,
canonicalise_options2(In, Out).
canonicalise_options(Options, Options).
canonicalise_options2([], []).
canonicalise_options2([H0|T0], [H|T]) :-
canonicalise_option(H0, H),
canonicalise_options2(T0, T).
canonicalise_option(Name=Value, H) :-
!,
H =.. [Name,Value].
canonicalise_option(Name-Value, H) :-
!,
H =.. [Name,Value].
canonicalise_option(H, H).
%! meta_options(+IsMeta, :Options0, -Options) is det.
%
% Perform meta-expansion on options that are module-sensitive.
% Whether an option name is module-sensitive is determined by
% calling call(IsMeta, Name). Here is an example:
%
% ==
% meta_options(is_meta, OptionsIn, Options),
% ...
%
% is_meta(callback).
% ==
%
% Meta-options must have exactly one argument. This argument will
% be qualified.
%
% @tbd Should be integrated with declarations from
% predicate_options/3.
meta_options(IsMeta, Context:Options0, Options) :-
is_dict(Options0),
!,
dict_pairs(Options0, Class, Pairs0),
meta_options(Pairs0, IsMeta, Context, Pairs),
dict_pairs(Options, Class, Pairs).
meta_options(IsMeta, Context:Options0, Options) :-
must_be(list, Options0),
meta_options(Options0, IsMeta, Context, Options).
meta_options([], _, _, []).
meta_options([H0|T0], IM, Context, [H|T]) :-
meta_option(H0, IM, Context, H),
meta_options(T0, IM, Context, T).
meta_option(Name=V0, IM, Context, Name=(M:V)) :-
call(IM, Name),
!,
strip_module(Context:V0, M, V).
meta_option(Name-V0, IM, Context, Name-(M:V)) :-
call(IM, Name),
!,
strip_module(Context:V0, M, V).
meta_option(O0, IM, Context, O) :-
compound(O0),
O0 =.. [Name,V0],
call(IM, Name),
!,
strip_module(Context:V0, M, V),
O =.. [Name,M:V].
meta_option(O, _, _, O).
%! dict_options(?Dict, ?Options) is det.
%
% Convert between an option list and a dictionary. One of the
% arguments must be instantiated. If the option list is created,
% it is created in canonical form, i.e., using Option(Value) with
% the Options sorted in the standard order of terms. Note that the
% conversion is not always possible due to different constraints
% and convertion may thus lead to (type) errors.
%
% - Dict keys can be integers. This is not allowed in canonical
% option lists.
% - Options can hold multiple options with the same key. This is
% not allowed in dicts.
% - Options can have more than one value (name(V1,V2)). This is
% not allowed in dicts.
%
% Also note that most system predicates and predicates using this
% library for processing the option argument can both work with
% classical Prolog options and dicts objects.
dict_options(Dict, Options) :-
nonvar(Dict),
!,
dict_pairs(Dict, _, Pairs),
canonicalise_options2(Pairs, Options).
dict_options(Dict, Options) :-
dict_create(Dict, _, Options).