[Haskell-cafe] Few Alex questions
golubovsky at gmail.com
Thu Apr 30 23:33:15 EDT 2009
Q1: I am trying to create an Alex equivalent of the following flex file:
http://code.haskell.org/yc2js/es-idl/lexer.ll (lexer for Web IDL which
is a dialect of OMG IDL)
I haven't been able to find Alex equivalent for the following line:
that is any amount of whitespace at the beginning of line followed by '#'
I defined a @WhiteSpace macro some place earlier, but Alex gives me
parser error on the line I created:
@PoundSign = ^@WhiteSpace*#
in the position 28 that is position of '@', next to caret, that is,
caret is not recognized by Alex.
Can beginning of line (caret) be recognized by Alex?
Q2: The original line says:
basically same as comments in C or Java.
I had to prefix star and slash even within square brackets with
backslashes to make it compile.
So I got:
@MultiLineComment = \/\*(([^\*])|(\*[^\/]))*\*\/
Is this correct understanding that if we want to match any character
except for an asterisk, then Alex would like to see [^\*] rather than
[^*]? And [^\/] rather than [^/]?
Or would it be better to use a hex code for the asterisk and slash?
Anywhere on the Web
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