Parsing escape characters

[duncanmak]

I've written a scanner for Postscript using a few of the examples as a guide, and I have the following code, but somehow, the escape characters are not working.

Parser string_() =>
    ref(bracket, '()', (ref(characterNoString) | ref(string_)).star().flatten())
    .pick(1)
    .map((s) {
      print(s);
      print(s.runes);
      return PSString.from(s);
    });

  // Parser character() => ref(characterEscape) | ref(characterRaw);
  Parser characterNoString() => (ref(characterEscape) | ref(characterRawNoString)).map((s) { print("Adding $s ${s.runes}"); return s; });
  Parser characterEscape() => (char('\\') & pattern(escapeCharacters.keys.join())).map((s) => escapeCharacters[s[1]]);
  Parser characterRaw() => pattern('^)');
  Parser characterRawNoString() => pattern('^(^)^\\');

  Parser name() => ref(literal) | ref(name_);
  Parser literal() => (char('/') & name_())
    .flatten("literal expected")
    .map((i) => PSName.Literal(i.substring(1)));

  static final Map<String, String> escapeCharacters = {
    '\\': '\\',
    '/': '/',
    '(': '(',
    ')': ')',
    'b': '\b',
    'f': '\f',
    'n': '\n',
    'r': '\r',
    't': '\t'
  };

When I run the scanner, I see this:

Adding * (42)
Adding * (42)
Adding * (42)
Adding E (69)
Adding R (82)
Adding R (82)
Adding O (79)
Adding R (82)
Adding * (42)
Adding * (42)
Adding * (42)
Adding 
 (10)
***ERROR***\n
(42, 42, 42, 69, 82, 82, 79, 82, 42, 42, 42, 92, 110)

Somehow, instead of the "\n" turning into charcode 10, it stays as 92, 110.

What am I doing wrong?

[renggli]

I think the problem is here: (ref(characterNoString) | ref(string_)).star().flatten(). flatten returns the consumed sub-string, so it ignores the decoded characters you return.

Probably something like ... .star().map((s) => s.join()) is what you want ...

[duncanmak]

Oh! Thanks so much for the help, that did the trick!