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xt_factorial(3) Library Functions Manual xt_factorial(3) NAME xt_factorial() - Fast factorial function LIBRARY #include <inttypes.h> #include <xtend/math.h> -lxtend SYNOPSIS uint64_t xt_factorial(unsigned n) ARGUMENTS n Integer in the range [0,20] (inclusive) for which n! is returned. DESCRIPTION Instantaneous factorial for n in [0,20] using a lookup table. Note that 21! is beyond the range of uint64_t, so programs that need it should either use a multiple precision library or rearrange the computa- tions to avoid repeated multiplication leading to overflow. xt_n_choose_k(3) uses the latter approach to avoid computing whole factori- als before finally dividing. RETURN VALUES n! if n is an element of [0,20], 0 otherwise EXAMPLES #include <inttypes.h> #include <xtend/math.h> printf("20! = %" PRIu64 "n", factorial(20)); FILES Environment SEE ALSO xt_factorial(3)
NAME | LIBRARY | SYNOPSIS | ARGUMENTS | DESCRIPTION | RETURN VALUES | EXAMPLES | FILES | SEE ALSO
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