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/* Part of SWI-Prolog
Author: Michael Hendricks
E-mail: michael@ndrix.org
WWW: http://www.swi-prolog.org
Copyright (C): 2013,2014, Michael Hendricks
All rights reserved.
Redistribution and use in source and binary forms, with or without
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
the documentation and/or other materials provided with the
distribution.
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 HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/
:- module(prolog_format,
[ format_spec/2, % +Format, -Spec
format_spec//1, % -Spec
format_types/2 % +Format, -Types
]).
:- use_module(library(dcg/basics), [eos//0, integer//1, string_without//2]).
:- use_module(library(when), [when/2]).
/** <module> Analyse format specifications
This library parses the format specification used by format/1, format/2
and format/3. The parsed specification can be used to validate the
consistency of the format string and the provided arguments. For
example:
==
?- format_types('~d bottles of beer', Types).
Types = [integer].
==
@tbd The current implementation does not support format_predicate/2.
@see http://www.swi-prolog.org/pack/list?p=format_spec
@author Michael Hendricks
*/
%% format_spec(+Format, -Spec:list) is semidet.
%
% Parse a format string. Each element of Spec is one of the following:
%
% * text(Text)
% Text sent to the output as is
% * escape(Num,Colon,Action)
% A format escape. Num represents the optional numeric portion of
% an esape. Colon represents the optional colon in an escape.
% Action is an atom representing the action to be take by this
% escape.
format_spec(Format, Spec) :-
when((ground(Format);ground(Codes)),text_codes(Format, Codes)),
once(phrase(format_spec(Spec), Codes, [])).
%% format_spec(-Spec)//
%
% DCG for parsing format strings. It doesn't yet generate format
% strings from a spec. See format_spec/2 for details.
format_spec([]) -->
eos.
format_spec([escape(Numeric,Modifier,Action)|Rest]) -->
"~",
numeric_argument(Numeric),
modifier_argument(Modifier),
action(Action),
format_spec(Rest).
format_spec([text(String)|Rest]) -->
{ when((ground(String);ground(Codes)),string_codes(String, Codes)) },
string_without("~", Codes),
{ Codes \= [] },
format_spec(Rest).
%% format_types(+Format:text, -Types:list) is det.
%
% True when Format requires an argument list with terms of the type
% specified by Types. The length of this list is the number of
% arguments required. Each value of Types is a type as described by
% error:has_type/2.
format_types(Format, Types) :-
format_spec(Format, Spec),
spec_types(Spec, Types).
%% spec_types(+FormatSpec, -Types:list(type)) is det.
%
% True if FormatSpec requires format/2 to have arguments of Types.
% Each value of Types is a type as described by error:has_type/2. This
% notion of types is compatible with library(mavis).
spec_types(Spec, Types) :-
phrase(spec_types(Spec), Types).
spec_types([]) -->
[].
spec_types([Item|Items]) -->
item_types(Item),
spec_types(Items).
item_types(text(_)) -->
[].
item_types(escape(Numeric,_,Action)) -->
numeric_types(Numeric),
action_types(Action).
numeric_types(number(_)) -->
[].
numeric_types(character(_)) -->
[].
numeric_types(star) -->
[number].
numeric_types(nothing) -->
[].
action_types(Action) -->
{ atom_codes(Action, [Code]) },
{ action_types(Code, Types) },
phrase(Types).
%% text_codes(Text:text, Codes:codes).
text_codes(Var, Codes) :-
var(Var),
!,
string_codes(Var, Codes).
text_codes(Atom, Codes) :-
atom(Atom),
!,
atom_codes(Atom, Codes).
text_codes(String, Codes) :-
string(String),
!,
string_codes(String, Codes).
text_codes(Codes, Codes) :-
is_of_type(codes, Codes).
numeric_argument(number(N)) -->
integer(N).
numeric_argument(character(C)) -->
"`",
[C].
numeric_argument(star) -->
"*".
numeric_argument(nothing) -->
"".
modifier_argument(colon) -->
":".
modifier_argument(no_colon) -->
\+ ":".
action(Action) -->
[C],
{ is_action(C) },
{ atom_codes(Action, [C]) }.
%% is_action(+Action:integer) is semidet.
%% is_action(-Action:integer) is multi.
%
% True if Action is a valid format/2 action character. Iterates all
% acceptable action characters, if Action is unbound.
is_action(Action) :-
action_types(Action, _).
%% action_types(?Action:integer, ?Types:list(type))
%
% True if Action consumes arguments matching Types. An action (like
% `~`), which consumes no arguments, has `Types=[]`. For example,
%
% ?- action_types(0'~, Types).
% Types = [].
% ?- action_types(0'a, Types).
% Types = [atom].
action_types(0'~, []).
action_types(0'a, [atom]).
action_types(0'c, [integer]). % specifically, a code
action_types(0'd, [integer]).
action_types(0'D, [integer]).
action_types(0'e, [float]).
action_types(0'E, [float]).
action_types(0'f, [float]).
action_types(0'g, [float]).
action_types(0'G, [float]).
action_types(0'i, [any]).
action_types(0'I, [integer]).
action_types(0'k, [any]).
action_types(0'n, []).
action_types(0'N, []).
action_types(0'p, [any]).
action_types(0'q, [any]).
action_types(0'r, [integer]).
action_types(0'R, [integer]).
action_types(0's, [text]).
action_types(0'@, [callable]).
action_types(0't, []).
action_types(0'|, []).
action_types(0'+, []).
action_types(0'w, [any]).
action_types(0'W, [any, list]).
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