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 _______________________________________________ Libraries mailing list [hidden email] http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries |
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 <[hidden email]> 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 > _______________________________________________ > Libraries mailing list > [hidden email] > http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries Libraries mailing list [hidden email] http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries |
That pretty much sums it up. On Sun, Mar 22, 2020, 17:55 chessai . <[hidden email]> wrote: Sure, I don't see why not. I think powModNatural is also safe. _______________________________________________ Libraries mailing list [hidden email] http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries |
Sounds reasonable to me. Perhaps others can weigh in. Thanks On Sun, Mar 22, 2020, 6:11 PM Zemyla <[hidden email]> wrote:
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