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─────Run-Time Library───────────────────────────────────────────────────────
 
     The log and log10 functions calculate the natural logarithm and
     base-10 logarithm of <x>, respectively.
 
     The _logl and _log10l functions use the 80-bit long double form of
     arguments and return values. In all other respects, they are
     identical to the regular functions.
 
     Return Value
 
     These functions return the logarithm result. If <x> is negative,
     the functions print a _DOMAIN error message to stderr, return the
     value -HUGE_VAL (or -_LHUGE_VAL for the long double functions),
     and set errno to EDOM. If <x> is 0, the functions print a _SING
     error message to stderr, return the value -HUGE_VAL (or
     -_LHUGE_VAL for the long double functions), and set errno to
     ERANGE.
 
     Error handling can be modified by using the _matherr (or
     _matherrl) routine.
                                    -♦-