is there any reason why float parses only positive numbers?
It is usual in parsing libraries to separate the recognition of a
leading sign from recognition of the number itself: the sign-only
parser can be reused in many contexts, e.g. in the Haskell'98 Numeric
library, there is
readSigned :: Real a => ReadS a -> ReadS a
which takes a secondary parser as its argument. You can instantiate
that argument to any of
readDec :: Num a => ReadS a
readHex :: Num a => ReadS a
readFloat :: Num a => ReadS a
etc. I do not know if the equivalent of "readSigned" exists in
Parsec, but it in polyparse's Text.Parse module, it is called
"parseSigned", rather unsurprisingly.
Regards,
Malcolm
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