That seems a really weird way to write it! Who decided all auxiliary functions should be called go? (I think I'm blaming dons) - why not:
sffi :: (Integral a,Num a) => Integer -> Maybe a sffi n | toInteger n2 == n = Just n2 | otherwise = Nothing where n2 = fromInteger n
I know I was too lazy to clean it up :-P ( I also blame Dons for 'go' )
I think the Common Lisp community tends to use 'foo-aux' instead of 'go' for these sort of axillary functions. But, then in Haskell we can't use hyphen as an identify character and underscore is not popular. For this reason I started using fooAux in Haskell, but after learning that a single quote is valid identifier character I started using foo'.
Other than using go and foo', what do people use in Haskell?
I use f, if I need several auxiliary functions I start at f and work my way up alphabetically. I tend to go back to f2 if I go past h. Be grateful you don't have to maintain my code :-) Thanks Neil PS. Here is some code from the filepath library I wrote, illustrating how fantastic my naming scheme looks. (I think if I was writing it today I'd have used a list comprehension for validChars, eliminating f.) makeValid path = joinDrive drv $ validElements $ validChars pth where (drv,pth) = splitDrive path validChars x = map f x f x | x `elem` badCharacters = '_' | otherwise = x validElements x = joinPath $ map g $ splitPath x g x = h (reverse b) ++ reverse a where (a,b) = span isPathSeparator $ reverse x h x = if map toUpper a `elem` badElements then a ++ "_" <.> b else x where (a,b) = splitExtensions x