Hello,

> Ignoring this, I think I can summarize:
>

> - Data.ByteString.Char8 has no performance penalty: "w2c" uses

> "unsafeChr" which is a no-op, and GHC.Word has a RULES pragma making the
> "fromIntegral" also free (it's a narrow8Word#)

> - for some reason GHC is generating worse code for the Word8 versions of

> toLower than it is for the Char equivalents

> - consequently, there seems to be no reason to use the word8 library:

> not only is it not faster, it's actually a pessimization.

My dictionary does not have the word "pessimization". Would you explain
what do you want to say with other words?

It's a joke on "optimization" (see "optimism" vs "pessimism"), in other words making things slower rather than faster.

Anyway, my understanding from this thread is:

- Data.ByteString.Char8 does not have performance penalty. So, we can
use the character literal (e.g. 'H') with it for code readability.

- But the utility functions in Data.Char is slow because it handles
Unicode. So, we need faster utility functions specialized to Char.

Is this correct? Should I implement the char8 library (or include
Data.Char8 in the word8 library)?

I know that Greg dislikes to have extra libraries but I think that
sharing utility functions is a good thing.