Export functions on Natural in Numeric.Natural

[chessai .]

Sounds reasonable to me. Perhaps others can weigh in.

Thanks

On Sun, Mar 22, 2020, 6:11 PM Zemyla <zemyla at gmail.com> wrote:

> That pretty much sums it up.
>
> On Sun, Mar 22, 2020, 17:55 chessai . <chessai1996 at gmail.com> wrote:
>
>> Sure, I don't see why not. I think powModNatural is also safe.
>>
>> Are your criteria for a function worth re-exporting from Numeric.Natural
>> that
>>
>> 1. The function does not have an overloaded variant defined in base
>> (e.g. all the monorphic version of `fromIntegral` in GHC.Natural would
>> be excluded) and
>> 2. The function is total?
>>
>> Thanks
>>
>> On Sun, Mar 22, 2020 at 11:40 AM Zemyla <zemyla at gmail.com> wrote:
>> >
>> > Functions in GHC.Natural like naturalToWordMaybe and minusNaturalMaybe
>> are extremely useful, especially when trying to write provably total
>> functions, and I wish they were available in a Safe module like
>> Numeric.Natural. I also want a total function that does the following:
>> >
>> > -- This function turns an Integer n into a pair of
>> > -- (fromInteger (abs n), fromInteger (signum n)).
>> > integerToNaturalSign :: Integer -> (Natural, Int)
>> > #if 0
>> > -- This is the reference version, except for the fact that numeric
>> literals don't exist yet
>> > -- when GHC.Natural is being defined, and fromInteger isn't actually
>> total.
>> > integerToNaturalSign n = case compare n 0 of
>> >   LT -> (fromInteger (negate n), -1)
>> >   EQ -> (0, 0)
>> >   GT -> (fromInteger n, 1)
>> > #elif !defined(MIN_VERSION_integer_gmp)
>> > -- This is like the reference version, except using the newtype wrapper
>> and MagicHash.
>> > integerToNaturalSign n = case compare n (intToInteger# 0#) of
>> >   LT -> (Natural (negateInteger n), I# (-1#))
>> >   EQ -> (Natural n, I# 0#)
>> >   GT -> (Natural n, I# 1#)
>> > #else
>> > -- We take advantage of the GMP functions and constructors.
>> > integerToNaturalSign (Jn# bn) = (bigNatToNatural bn, I# (-1#))
>> > integerToNaturalSign (S# i#) = case isTrue# (i# <# 0#) of
>> >   True -> (NatS# (int2Word# (negateInt# i#)), I# (-1#))
>> >   _    -> (NatS# (int2Word# i#), I# (i# ># 0#))
>> > integerToNaturalSign (Jp# bn) = (bigNatToNatural bn, I# 1#)
>> > #endif
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>>
>
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