I finished a draft version of pipes-text with
the 'lens' approach.
https://github.com/michaelt/text-pipes/tree/master/Pipes
I think I am following
Gabriels advice above, more or less, by
just giving functions like
encodeIso8859_1 :: Monad m
=> Producer Text m r
-> Producer ByteString m (Producer Text m r)
decodeAscii :: Monad m
=> Producer ByteString m r
-> Producer Text m (Producer ByteString m r)
in each direction. For utf8 there is a
Lens of the type we wanted
decodeUtf8 :: Monad m
=> Lens' (Producer ByteString m r)
(Producer Text m (Producer ByteString m
r))
At the moment for I am replicating
the method of the enumerator and
conduit packages in defining `Codecs`
`utf16_le` , `utf16_be` , `utf32_le` ,
`utf32_be` and then a function that
makes a Lens' for them
codec :: Monad m
=> Codec
-> Lens' (Producer ByteString m r)
(Producer Text m (Producer ByteString m r))
(there is also such a `Codec` for utf8).
In all cases, we do without the customary
`Text` exception system. When decoding or
encoding of a `Producer ByteString ...` or
`Producer Text ...` goes wrong, we simply
return the remaining Producer we are
encoding or decoding. Or that is what I think
I am doing. I can't tell if it's insane or not.
I was thinking of replacing the `Codecs` with
a series of individual lenses later; I am for
the moment using them to take advantage of
the presumed correctness of the code
I am modifying. (I don't like the way
the original code is written, but no matter for
the moment.)
I decided that all IO in the module should
be `Pipes.Prelude` -like in character and
that this should be emphasized.
Everything is done on the basis of
things in `Data.Text.IO` and the like;
it all uses `Text`'s exception machinery
and is a little slow.
So I will advertise that `Pipes.ByteString`
and co. defines the "real" IO operations,
which are about 3 times as fast, and
which we textify with `encodeUtf8`
and `decodeUtf8` and the like.
I was wondering if the 'api' of the `Pipes.Text`
module now seems more or less what is desirable
so I could hackage it pretty soon as version 0.0.0
(The way some things are implemented
is perhaps objectionable, except where I
am replicating `Pipes.ByteString`)
yours ever, Michael
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