[Haskell-cafe] Num instance for Lazy ByteStrings (was:
NumLazyByteString Package License)
schlepptop at henning-thielemann.de
Wed Mar 10 06:16:12 EST 2010
Yitzchak Gale schrieb:
> Henning Thielemann wrote:
>>> Is NumLazyByteString a newtype around Bytestring.Lazy
>>> that interprets the bit stream represented by the ByteString
>>> as integer?
> Thomas DuBuisson wrote:
>> Not exactly. There is not newtype wrapper. NumLazyByteString is:
>> instance Num L.ByteString where
> Are you absolutely certain that this is the one and only
> canonical instance that can ever exist that makes sense?
> Otherwise, please use a newtype wrapper.
I think there are at least two reasonable instance: One that treats all
bytes individually and one that treats the whole bytestring as one
Btw. I assume that in order to be lazy when computing exactly with
integers you must start with the least significant bits, right? In my
implementation of Positional numbers I start with the most significant
digits since I implemented fractional numbers and I must use a redundant
set of digits in order to stay lazy in case of carries.
> The reason for this is one of the few remaining major warts
> in Haskell - that there is absolutely *no way* to
> prevent the export of instances from a module that you import.
Since this is a common issue a wrote a Wiki article on it:
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