:: x -> (x, x)

Duplicate a single value into a pair.

dupe 12 == (12, 12)

Construct a pair by duplication of a single value

Known as dup in the Arrow literature.

Creates a tuple by pairing something with itself.

>>> dup "foo"
("foo","foo")

>>> dup ()
((),())

Duplicate an input.

\x -> (x::Rational) == (uncurry (+) $ mapFst fromInteger $ splitFraction x)

\x -> uncurry (==) $ mapFst (((x::Double)-) . fromInteger) $ splitFraction x

\x -> uncurry (==) $ mapFst (((x::Rational)-) . fromInteger) $ splitFraction x

\x -> splitFraction x == (floor (x::Double) :: Integer, fraction x)

\x -> splitFraction x == (floor (x::Rational) :: Integer, fraction x)

RealRing.genericSplitFraction =~= (NP.splitFraction :: Double -> (Integer,Double))

RealRing.genericSplitFraction =~= (NP.splitFraction :: Rational -> (Integer,Rational))

Splits the argument into its prime prefix and the remaining suffix. Returns Nothing for mempty.

Splits the argument into its prime suffix and the remaining prefix. Returns Nothing for mempty.

Attempt to extract the left-most element from a container, and a version of the container without that element.

>>> uncons []
Nothing

>>> uncons [a, b, c]
Just (a,[b,c])

Attempt to extract the left-most element from a container, and a version of the container without that element.

>>> uncons []
Nothing

>>> uncons [1, 2, 3]
Just (1,[2,3])

Attempt to extract the right-most element from a container, and a version of the container without that element.

>>> unsnoc (LazyT.pack "hello!")
Just ("hello",'!')

>>> unsnoc (LazyT.pack "")
Nothing

>>> unsnoc (Seq.fromList [b,c,a])
Just (fromList [b,c],a)

>>> unsnoc (Seq.fromList [])
Nothing

Attempt to extract the right-most element from a container, and a version of the container without that element.

>>> unsnoc "hello!"
Just ("hello",'!')

>>> unsnoc ""
Nothing

Extract head and tail, return Nothing if empty