gamma(3m) — DG/UX 4.00



                                                                gamma(3m)



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        gamma
        log gamma function
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        SYNTAX

        #include <math.h>

        double gamma (x)
        double x;

        extern int signgam;


        DESCRIPTION
                                                             oo
        Gamma returns ln(|Γ~(x)|), where Γ~(x) is defined as ∫ e-ttx-1dt.
        The sign of Γ~(x) is returned in the external integer0signgam.
        The argument x must be a non-negative integer.

        The following C program fragment might be used to calculate Γ~:

             if ((y = gamma(x)) > LN_MAXDOUBLE)
                  error();
             y = signgam * exp(y);

        LN_MAXDOUBLE is the least value that causes exp(3M) to return a
        range error, and is defined in the <values.h> header file.


        DIAGNOSTICS

        For non-negative integer arguments HUGE is returned, and errno is
        set to EDOM.  A message indicating SING error is printed on the
        standard error output.

        If the correct value would overflow, gamma returns HUGE and sets
        errno to ERANGE.

        You can change these error-handling procedures with the function
        matherr(3M).


        SEE ALSO

        exp(3M), matherr(3M), values(5).






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