Whitespaces and line in BYacc - parsing

Question

Hy guys.
What do you think about these two rules to parse whitespaces and to recognize the different lines of the file I must translate?
1.
line: NEW_LINE {$$ = System.lineSeparator();}
| line NEW_LINE {$$ = $1 + System.lineSeparator();}
where:
NEW_LINE = \r\n|\n|\r in Jflex
2.
whitespace: WHITESPACE {$$ = " ";}
| whitespace WHITESPACE {$$ = $1 + " ";}
where:
WHITESPACE = [ \t] in Jflex
Are they correct? Thanks of all

Answer 1

line: NEW_LINE {$$ = System.lineSeparator();}
| line NEW_LINE {$$ = $1 + System.lineSeparator();}
where:
NEW_LINE = \r\n|\n|\r in Jflex
If you don't really care about multliple newlines, as this grammar suggests, collect them all in the lexer:
NEW_LINE = (\r\n|\n|\r)+ return NEW_LINE;
and not in the parser:
line : NEW_LINE { $$ = System.lineSeparator(); }
Whitespace normally includes line terminators, unless they are significant in your grammar, which they seem to be, but also formfeeds:
WHITESPACE [ \t\f]
and again it is much more efficient to collect it all in the lexer rather than the parser:
WHITESPACE [ \t\f]+
whitespace: WHITESPACE { $$ = strdup(yytext); }
Note that this has to be free()-d whenever it reappears as $1, $2, etc, and isn't copied directly to $$.
But then usually whitespace doesn't appear in the grammar at all, it is just ignored by the lexer:
WHITESPACE [ \t\f]+ ;
unless again you really really need it in the grammar. This is pretty unlikely. You should just be able to work with the non-whitespace tokens the lexer returns to you.