[web-devel] Data.Word8 (word8 library)

Kazu Yamamoto ( 山本和彦 ) kazu at iij.ad.jp
Fri Sep 21 05:11:11 CEST 2012


> 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?

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.


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