[clean-list] Does (<!?>) mean the element is optional?
metaperl
metaperl at gmail.com
Tue Aug 26 20:09:19 MEST 2008
The docs for (<!?>) say:
// takes an element if it is there
<!?> :: (Parser s r t) (r -> u) u -> Parser s u t
So I'm wondering if that means this parse always succeeds even if what it is
looking for is not there. Concretely, in the case below it would mean: "The
Date and Time Prefix is entirely optional and the parse continues without
error, even if it is not found"
// metar prefix
metarPrefix :: Parser [Char] Char t
metarPrefix = "Date and Time Prefix (four or six digits followed by Z)" :>
(word p)
where p = twoDigits &> twoDigits &> (<!?> twoDigits undef undef) &> (symbol
'Z')
// metar
metar :: Parser [Char] MetarData t
metar = (<!?> metarPrefix undef undef) &> metarData
--
View this message in context: http://www.nabble.com/Does-%28%3C%21-%3E%29-mean-the-element-is-optional--tp19167295p19167295.html
Sent from the Clean mailing list archive at Nabble.com.
More information about the clean-list
mailing list