Takes two arguments a and b, and returns the base-a logarithm of b.
Format: Log(exp1, exp2)
Arguments:
Return type: float
Error conditions: Returns 'Bottom' if either of exp1 or exp2 evaluates to 'Bottom', or if either of exp1 or exp2 is not positive.
Example:
value = log(2, 64)
; Sets value to the base 2 log of 64, which is 6.0.