'Returns e ** a.
>>> c = ExtendedContext.copy()
>>> c.Emin = -999
>>> c.Emax = 999
>>> c.exp(Decimal(\'-Infinity\'))
Decimal(\'0\')
>>> c.exp(Decimal(\'-1\'))
Decimal(\'0.367879441\')
>>> c.exp(Decimal(\'0\'))
Decimal(\'1\')
>>> c.exp(Decimal(\'1\'))
Decimal(\'2.71828183\')
>>> c.exp(Decimal(\'0.693147181\'))
Decimal(\'2.00000000\')
>>> c.exp(Decimal(\'+Infinity\'))
Decimal(\'Infinity\')
>>> c.exp(10)
Decimal(\'22026.4658\')'

def exp(self, a):

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