+ -- | Absolute value.
+ abs :: a -> a
+ -- | Sign of a number.
+ -- The functions 'abs' and 'signum' should satisfy the law:
+ --
+ -- > abs x * signum x == x
+ --
+ -- For real numbers, the 'signum' is either @-1@ (negative), @0@ (zero)
+ -- or @1@ (positive).
+ signum :: a -> a
+ -- | Conversion from an 'Integer'.
+ -- An integer literal represents the application of the function
+ -- 'fromInteger' to the appropriate value of type 'Integer',
+ -- so such literals have type @('Num' a) => a@.