On Sat, Jan 21, 2012 at 09:34:26AM -0800, Carl Worth wrote:
> The trick here is that flex always chooses the rule that matches the most
> text. So with a input text of "two:" which we want to be lexed as an
> IDENTIFIER token "two" followed by an OTHER token ":" the previous OTHER
> rule would match longer as a single token of "two:" which we don't want.
>
> We prevent this by forcing the OTHER pattern to never match a string which
> has a first character that could be an identifier (that is _, a-z, or A-Z).
> This way the ambiguity is eliminated and this case is lexed correctly.
> ---
> src/glsl/glcpp/glcpp-lex.l | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/src/glsl/glcpp/glcpp-lex.l b/src/glsl/glcpp/glcpp-lex.l
> index 8661887..20d7fc1 100644
> --- a/src/glsl/glcpp/glcpp-lex.l
> +++ b/src/glsl/glcpp/glcpp-lex.l
> @@ -70,7 +70,7 @@ HSPACE [ \t]
> HASH ^{HSPACE}*#{HSPACE}*
> IDENTIFIER [_a-zA-Z][_a-zA-Z0-9]*
> PUNCTUATION [][(){}.&*~!/%<>^|;,=+-]
> -OTHER [^][(){}.&*~!/%<>^|;,=#[:space:]+-]+
> +OTHER
> [^][_a-zA-Z(){}.&*~!/%<>^|;,=#[:space:]+-][^][(){}.&*~!/%<>^|;,=#[:space:]+-]*
The fix seems correct, but reading that regex made my head hurt. Is
there a way to refactor the character classes to be more readable?
OTHER is basically
[{PUNCTUATION}{IDENTIFIER_FIRST_CHAR}[:space:]][{PUNCTUATION}[:space:]]*,
right?
> DIGITS [0-9][0-9]*
> DECIMAL_INTEGER [1-9][0-9]*[uU]?
> --
> 1.7.8.3
>
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