"Lou Pecora" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] | In article <[EMAIL PROTECTED]>, | "Terry Reedy" <[EMAIL PROTECTED]> wrote: | | > "Luis Zarrabeitia" <[EMAIL PROTECTED]> wrote in message | > news:[EMAIL PROTECTED] | > | Btw, there seems to be a math problem in python with exponentiation... | > | >>> 0**0 | > | 1 | > | That 0^0 should be a nan or exception, I guess, but not 1. | > | > a**b is 1 multiplied by a, b times. 1 multiplied by 0 no times is 1. | > But there are unenlighted people who agree with you ;-) | > Wikipedia has a discussion of this. | > | > tjr | | I like that argument better. But... | | I've also heard the very similar a**b is a multiplied by a b-1 times.
Me too, in school, but *that* definition is incomplete: it excludes b=0 and hence a**0 for all a. It was the best people could do before 0 was known. But 0 was introduced to Europe just over 800 years ago ;-) In general, sequence reduction work better if the base case is given separately rather that defined as the first member of the sequence (which excludes empty sequences!). ab = [a]*b # b a count a**b = reduce(int.__mul__, ab, 1) # better a**b = reduce(int.__mul__, ab[1:], a) # crashes for b=0 Consider the equivalent pair of definitions for a*b: a*b = 0 incremented by a, b times = reduce(int.__add__, ab, 0) a*b = a incremented by a, b-1 times = reduce(int.__add__, ab[1:] a) Since we have 0, the second, which excludes (crashes on) a*0 , is incomplete. Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
