js_grammar.pl

/*  Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        J.Wielemaker@vu.nl
    WWW:           http://www.swi-prolog.org
    Copyright (c)  2013-2016, VU University Amsterdam
    All rights reserved.

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*/

:- module(javascript_grammar,
          [ js_token//1
          ]).
:- use_module(library(dcg/basics)).
:- use_module(library(pure_input)).     % syntax_error//1
:- set_prolog_flag(double_quotes, codes).

/** <module> JavaScript grammar

This file provides a tokenizer for   JavaScript  (EcmaScript). This code
supports  the  quasi  quotation   syntax    =javascript=,   defined   in
library(http/js_write).

@see    http://tomcopeland.blogs.com/EcmaScript.html is used for the
        high-level syntax.
@see    http://www.ecma-international.org/ecma-262/5.1/ is used for
        implementing the tokenization code.
*/

%!  js_token(-TokenType)//
%
%   Matches and classifies the next JavaScript token.

js_token(Type) -->
    token(Type).

%!  token(-Type) is semidet.
%
%   Get the next token from the   input. Fails when encountering the
%   end of the input.
%
%   @error syntax_error(Culprit)

token(comment)        --> comment, !.
token(string)         --> string_literal, !.
token(number)         --> numeric_literal, !.
token(identifier(Id)) --> identifier_name(Id), !.
token(regex)          --> regex_literal, !.
token(ws)             --> blank, !, blanks.
token(punct(Char))    --> [Code], { char_code(Char, Code) }.

%!  comment// is semidet.

comment -->
    "/*",
    !,
    (   string(_), "*/"
    ->  []
    ;   syntax_error(eof_in_comment)
    ).
comment -->
    "//",
    !,
    (   string(_), eol
    ->  []
    ;   string(_), eof
    ->  []
    ).


%!  string_literal// is semidet.
%
%   Matches a string literal

string_literal -->
    "\"",
    !,
    (   q_codes, "\""
    ->  []
    ;   syntax_error(eof_in_string)
    ).
string_literal -->
    "\'",
    !,
    (   q_codes, "\'"
    ->  []
    ;   syntax_error(eof_in_string)
    ).


%!  numeric_literal//
%
%   Matches JavaScript notion of a numeric constant

numeric_literal -->
    (   decimal_literal
    ->  []
    ;   hex_integer
    ),
    (   (   decimal_digit
        ;   js_id_start(_)
        )
    ->  syntax_error(js(illegal_number))
    ;   []
    ).

decimal_literal -->
    decimal_integer, ".", opt_decimal_digits, opt_exponent.
decimal_literal -->
    ".", decimal_digits, opt_exponent.
decimal_literal -->
    decimal_integer,
    opt_exponent.

decimal_integer -->
    "0",
    !.
decimal_integer -->
    non_zero_digit, opt_decimal_digits.

decimal_digits -->
    decimal_digit,
    !,
    opt_decimal_digits.

opt_decimal_digits -->
    decimal_digit,
    !,
    opt_decimal_digits.
opt_decimal_digits -->
    [].

decimal_digit --> [C], { code_type(C, digit) }.
non_zero_digit --> [C], { code_type(C, digit), C \== 0'0 }.

opt_exponent -->
    exponent,
    !.
opt_exponent -->
    [].

exponent -->
    exponent_indictor,
    signed_integer.

exponent_indictor --> "e", !.
exponent_indictor --> "E".

signed_integer --> "+", !, decimal_digits.
signed_integer --> "-", !, decimal_digits.
signed_integer -->         decimal_digits.

hex_integer --> "0", x, hex_digit, hex_digits.

x --> "x".
x --> "X".


%!  regex_literal// is semidet.
%
%   Matches regex expression /.../flags

regex_literal -->
    "/", regex_body, "/", !, regex_flags.

regex_body -->
    regex_first_char,
    regex_chars.

regex_chars --> regex_char, !, regex_chars.
regex_chars --> [].

regex_first_char -->
    regex_backslash_sequence.
regex_first_char -->
    regex_non_terminator(C),
    !,
    { \+ memberchk(C, "*\\/[") }.
regex_first_char -->
    regex_class.

regex_char -->
    regex_backslash_sequence.
regex_char -->
    regex_non_terminator(C),
    !,
    { \+ memberchk(C, "\\/[") }.
regex_char -->
    regex_class.

regex_backslash_sequence -->
    "\\", !, regex_non_terminator(_).

regex_class -->
    "[", regex_class_chars, "]".

regex_class_chars --> regex_class_char, !, regex_class_chars.
regex_class_chars --> "".

regex_class_char -->
    regex_non_terminator(C),
    !,
    { \+ memberchk(C, "]\\") }.

regex_non_terminator(_) -->
    eol, !, {fail}.
regex_non_terminator(C) -->
    source_char(C).

regex_flags -->
    js_id_conts(_).

source_char(C) -->
    [C].


%!  q_codes//
%
%   Shortest list of quoted characters.

q_codes --> [] ; q_code, q_codes.

q_code --> "\\", !, char_esc.
q_code --> eol, !, {fail}.
q_code --> [_].

char_esc --> single_escape_char, !.
char_esc --> "x", !, hex_digit, hex_digit.
char_esc --> "u", !, hex_digit, hex_digit, hex_digit, hex_digit.
char_esc --> eol, !.

hex_digits --> hex_digit, !, hex_digits.
hex_digits --> [].

hex_digit --> [C], {code_type(C, xdigit(_))}.

single_escape_char --> "'".
single_escape_char --> "\"".
single_escape_char --> "\\".
single_escape_char --> "b".
single_escape_char --> "f".
single_escape_char --> "n".
single_escape_char --> "r".
single_escape_char --> "t".
single_escape_char --> "v".

eof -->
    \+ [_].


%       js_identifier classification. Now  based  on   Prolog.  This  is
%       pretty close, but I'm afraid there are corner cases.

identifier_name(Id) -->
    js_id_start(C0),
    !,
    js_id_conts(Rest),
    { atom_codes(Id, [C0|Rest]),
      (   keyword(Id)
      ->  fail, syntax_error(reserved(Id))
      ;   true
      )
    }.


js_id_start(C) --> [C], {js_id_start(C)}.

js_id_start(C) :- code_type(C, prolog_var_start), !.
js_id_start(C) :- code_type(C, prolog_atom_start), !.
js_id_start(0'$).

js_id_conts([H|T]) --> js_id_cont(H), !, js_id_conts(T).
js_id_conts([]) --> [].

js_id_cont(C) --> [C], {js_id_cont(C)}.

js_id_cont(C) :- code_type(C, prolog_identifier_continue), !.
js_id_cont(0'$) :- !.


keyword(break).                         % standard keywords
keyword(do).
keyword(instanceof).
keyword(typeof).
keyword(case).
keyword(else).
keyword(new).
keyword(var).
keyword(catch).
keyword(finally).
keyword(return).
keyword(void).
keyword(continue).
keyword(for).
keyword(switch).
keyword(while).
keyword(debugger).
keyword(function).
keyword(this).
keyword(with).
keyword(default).
keyword(if).
keyword(throw).
keyword(delete).
keyword(in).
keyword(try).

keyword(class).                         % reserved keywords
keyword(enum).
keyword(extends).
keyword(super).
keyword(const).
keyword(export).
keyword(import).

keyword(implements).                    % future reserved keywords
keyword(let).
keyword(private).
keyword(public).
keyword(yield).
keyword(interface).
keyword(package).
keyword(protected).
keyword(static).