Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaagh! Ok, that said, now I can explain my self a little more clearly. I am almost to the point of exasperation on trying to know when and why and how to convert between String, ByteString, ByteString.Laz, Char8 etc. For heavens sake how many bloody string types can you need? LOL I am trying to use Data.Digest.Pure.SHA but it takes a ByteString in the "sha1" function but from the command prompt of ghci I cannot seem to work out how to do it, I just get the usual daunting messages. sha1 :: ByteString -> Digest SHA1State I have a String, but the pack function wants a [Word8] to create a digest value. pack :: [Word8] -> ByteString IIUC, String is just [Char] and that Char is in fact a Unicode character and therefore NOT "8 bit" as such which is why the Char8 variants exist. I understand the difference between lazy and strict and why one is different from the other. But... it's little things like the foldr' function NOT being present in one library but present in the other, presumably a lazy implementation doesn't need a strict function or something like that. Who knows. I don't! I am sure to "seasoned" haskellers this is all elementary and I would love to eventually become a seasoned developer of it too but at times like this I want to scream in utter confusion as to how many different string types there are and the sometimes almost unnotcable differences between them. And trying to convert between them to actually get on and write useful working code. When do I use strict? When do I use lazy? When do I use the Char8 variant? And so the questions continue with barely any "beginner" level answers to be found. I'd write them myself but I don't know the answers yet! Speaking as a non-academic, non-mathemetician, but as a developer with 25+ years of using lots of languages inclusing Erlang, LISP and Scala, sometimes Haskell is very very hard to perservere with because everybody just seems to love using words and phrases like "mono-morphism", "monadic transformers" etc. just to show off how well they understand Haskell. That's fine for those in the club but those on the outside looking in would also like to be able to "get in" as well and be able to write serious looking blog posts about how damned funky haskell is. And it is... but not if you can't understand it! is there some kind of Free Masonry involved ;) Thanks again, Sean... now where's my RWH book again...