The IEEE 754 spec defines the following inputs as special:

For the pown function (integral exponents only):

• pown (x, 0) is 1 for any x (even a zero, quiet NaN, or infinity)
• pown (±0, n) is ±∞ and signals the divideByZero exception for odd integral n < 0
• pown (±0, n) is +∞ and signals the divideByZero exception for even integral n < 0
• pown (±0, n) is +0 for even integral n > 0
• pown (±0, n) is ±0 for odd integral n > 0.

For the pow function (integral exponents get special treatment):

• pow (x, ±0) is 1 for any x (even a zero, quiet NaN, or infinity)
• pow (±0, y) is ±∞ and signals the divideByZero exception for y an odd integer < 0
• pow (±0, −∞) is +∞ with no exception
• pow (±0, +∞) is +0 with no exception
• pow (±0, y) is +∞ and signals the divideByZero exception for finite y < 0 and not an odd integer
• pow (±0, y) is ±0 for finite y > 0 an odd integer
• pow (±0, y) is +0 for finite y > 0 and not an odd integer
• pow (−1, ±∞) is 1 with no exception
• pow (+1, y) is 1 for any y (even a quiet NaN)
• pow (x, y) signals the invalid operation exception for finite x < 0 and finite non-integer y.

For the powr function (derived by considering only exp(y * log(x))):

• powr (x, ±0) is 1 for finite x > 0
• powr (±0, y) is +∞ and signals the divideByZero exception for finite y < 0
• powr (±0, −∞) is +∞
• powr (±0, y) is +0 for y > 0
• powr (+1, y) is 1 for finite y
• powr (x, y) signals the invalid operation exception for x < 0
• powr (±0, ±0) signals the invalid operation exception
• powr (+∞, ±0) signals the invalid operation exception
• powr (+1, ±∞) signals the invalid operation exception
• powr (x, qNaN) is qNaN for x ≥ 0
• powr (qNaN, y) is qNaN.

However, the current implementation does not return the correct values for a number of these inputs (especially around the handling of NaN).