Could you offer a specific use case? When I need to convert a number
to its representation in some base, it’s because I’m displaying or
serialising it. A base is a notation (or a variant of a notation) and
it seems sensible to represent such notations with characters.
This raises another question: why is the base parameter overloaded?
base’s implementation of showIntAtBase uses quotRem on the base and
the number, but it could easily cast the base from Int. I imagine the
answer is “historical accident”.
On Sun, Apr 5, 2015 at 9:46 AM, Vikas Menon
Hi,
The current implementation of showIntAtBase in Numeric is limited to Chars currently.
showIntAtBase :: (Integral a, Show a) => a -> (Int -> Char) -> a -> ShowS
The 2 reasons for this constraint is: a) We only accept functions of the form (Int -> Char) b) An implicit concatenation using (:)
I'd like to propose a new function showIntAtBaseGeneric that removes the (Int -> Char) function constraint and takes an additional function to replace the implicit (:) operator.
showIntAtBaseGeneric :: (Integral a1, Num b, Show a1) => a1 -> (b -> a) -> (a -> s -> s) -> a1 -> s -> s
Now showIntAtBase may be implemented as:
showIntAtBase :: (Integral a, Show a) => a -> (Int -> Char) -> a -> ShowS showIntAtBase base toChr n0 r0 = showIntAtBaseGeneric base toChr (:) n0 r0
The API and behavior of showIntAtBase remains unchanged while allowing for generic conversions not limited to Chars alone.
Example: λ> showIntAtBaseGeneric 26 id (:) 500 [] -- convert 500 to base26 and provide output as a list. [19,6]
Please let me know thoughts/concerns if any to this proposal.
Cheers, Vikas
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