Re: Issues with factorial operator
От | Cui Shijun |
---|---|
Тема | Re: Issues with factorial operator |
Дата | |
Msg-id | 306760850706090320i72b45438vc3f6725b8d8318ab@mail.gmail.com обсуждение исходный текст |
Ответ на | Re: Issues with factorial operator ("Dann Corbit" <DCorbit@connx.com>) |
Список | pgsql-hackers |
yeah, simple and correct, I like that. :-) 2007/6/9, Dann Corbit <DCorbit@connx.com>: > > -----Original Message----- > [snip] > > Hum... I think there is a little improvement: when n is too large,(say > > n>10, 000) we can use Stirling's formula to get the estimated value of > > n! :-) > > Or (rather) the log base 10 of Stirling's formula. The n! estimator > will overflow for sure, unless we take the log of it. > > Rather than all that, why not just figure out what the largest number of > digits we will allow is and then don't allow inputs that will generate > more than that. > > The program I gave could be run with the target accuracy as the break > out of the loop and then the test would be: > > <type> factorial(<type> n) > { > if (n > CONSTANT_PRECOMPUTED_LIMIT) > return NULL; > else > { > return compute_actual_factorial(n); > } > } >
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