'Returns the natural (base e) logarithm of the operand.
>>> c = ExtendedContext.copy()
>>> c.Emin = -999
>>> c.Emax = 999
>>> c.ln(Decimal(\'0\'))
Decimal(\'-Infinity\')
>>> c.ln(Decimal(\'1.000\'))
Decimal(\'0\')
>>> c.ln(Decimal(\'2.71828183\'))
Decimal(\'1.00000000\')
>>> c.ln(Decimal(\'10\'))
Decimal(\'2.30258509\')
>>> c.ln(Decimal(\'+Infinity\'))
Decimal(\'Infinity\')
>>> c.ln(1)
Decimal(\'0\')'

def ln(self, a):

    a = _convert_other(a, raiseit=True)
    return a.ln(context=self)
