Question

我有以下背景,在文稿中可以免费打克。 txt

S ::= a S b
S ::= []

I m opening this file and able to read each line in prolog. Now i want to tokenize each line and generate a list such as

L=[[ S , ::= , a , S , b ],[ S , ::= , # ]]  ( #  represents empty)

如何做到这一点?

Answer 1

撰写《发展中国家概况》。我给你基本的(未测试的),你需要加以完善。

parse_grammar([Rule|Rules]) -->
 parse_rule(Rule),
 parse_grammar(Rules).
parse_grammar([]) --> [].

parse_rule([NT,  ::=  | Body]) -->
  parse_symbol(NT),
  skip_space,
  "::=",
  skip_space,
  parse_symbols(Body),
  skip_space, !.  % the cut is required if you use findall/3 (see below)

parse_symbols([S|Rest]) -->
  parse_symbol(S),
  skip_space,
  parse_symbols(Rest).
parse_symbols([]) --> [].

parse_symbol(S) -->
  [C], {code_type(C, alpha), atom_codes(S, [C])}.

skip_space -->
  [C], {code_type(C, space)}, skip_space.
skip_space --> [].

利用这一顶级:

  ...,
  read_file_to_codes( grammar.txt , Codes),
  phrase(parse_grammar(Grammar), Codes, [])).

你说,你当时读到档案1行:然后使用

  ...
  findall(R, (get_line(L), phrase(parse_rule(R), L, [])), Grammar).

HTH

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