Lazy Peano numbers including observable infinity value.
Note that the following equation does not hold for this number type:
1 + a > a, because
1 + infinity == infinity.
The following operation is undefined:
infinity - infinity
There are variants of
(-) with different behaviour regarding this, see below.
The following operations are naturally undefined:
0 - n, if
n > 0
fromInteger n, if
n < 0
toEnum n, if
n < 0
Natural numbers and infinity.
Difference of two natural numbers: the result is either positive or negative.
zeroDiff infinity infinity == Left 0.
infDiff infinity infinity == Left infinity.