Factorial as of now accepts only integers or integral floats. 
I want to suggest extending the definition of float to accept all positive real numbers to be more consistent with general definition of factorial that uses gamma function.

What I am proposing is:
1. for integer value, the function should work as it does and return integer result.

2. for float input, both integer and non-integer valued, the returned value should be a floating point number.

3. the input domain should be extended to all real numbers except negative integers.

Such generalized function would feel more mathematically consistent.