"Simon Peyton-Jones"
Ah yes, this is a genuine bug. Haskell 98 changed at some point to allow identifiers and field labels with a leading '_', but the library didn't keep pace.
I believe the fix for 'lex' is something like the following. Regards, Malcolm diff -u -r1.5 Lex.hs --- src/prelude/PreludeText/Lex.hs 2001/11/09 17:19:06 1.5 +++ src/prelude/PreludeText/Lex.hs 2003/02/10 12:30:00 @@ -26,13 +26,14 @@ lex (c:s) | isSingle c = [([c],s)] | isSym c = [(c:sym,t) | (sym,t) <- [span isSym s]] - | isAlpha c = [(c:nam,t) | (nam,t) <- [span isIdChar s]] + | isIdInit c = [(c:nam,t) | (nam,t) <- [span isIdChar s]] | isDigit c = [(c:ds++fe,t) | (ds,s) <- [span isDigit s], (fe,t) <- lexFracExp s ] | otherwise = [] -- bad character where - isSingle c = c `elem` ",;()[]{}_`" + isSingle c = c `elem` ",;()[]{}`" isSym c = c `elem` "!@#$%&*+./<=>?\\^|:-~" + isIdInit c = isAlpha c || c == '_' isIdChar c = isAlphaNum c || c `elem` "_'" lexFracExp ('.':c:s) | isDigit c