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Possible Duplicate:
Prove $0! = 1$ from first principles

Why does $0! = 1$?

All I know of factorial is that $x!$ is equal to the product of all the numbers that come before it. The product of 0 and anything is $0$, and seems like it would be reasonable to assume that $0! = 0$. I'm perplexed as to why I have to account for this condition in my factorial function (Trying to learn Haskell). Thanks.

  • 0
    This can be answered by a simple google search.2011-03-06
  • 4
    Possible duplicate: http://math.stackexchange.com/questions/20969/prove-0-1-from-first-principles2011-03-06
  • 0
    Dear Orbit, please refer to the question linked to above on this website.2011-03-06

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