26.04.13 18:50, Larry Hastings написав(ла):
On 04/26/2013 12:34 AM, Greg Ewing wrote:
Or if, as Guido says, the only sensible things to use
as enum values are ints and strings, just leave anything
alone that isn't one of those.
The standard Java documentation on enums:
http://docs.oracle.com/javase/tutorial/java/javaOO/enum.html
has an example enum of a "Planet", a small record type containing mass
and radius--each of which are floats. I don't know whether or not it
constitutes good programming, but I'd be crestfallen if Java enums were
more expressive than Python enums ;-)
This example requires more than features discussed here. It requires an
enum constructor.
class Planet(Enum):
MERCURY = Planet(3.303e+23, 2.4397e6)
VENUS = Planet(4.869e+24, 6.0518e6)
EARTH = Planet(5.976e+24, 6.37814e6)
MARS = Planet(6.421e+23, 3.3972e6)
JUPITER = Planet(1.9e+27, 7.1492e7)
SATURN = Planet(5.688e+26, 6.0268e7)
URANUS = Planet(8.686e+25, 2.5559e7)
NEPTUNE = Planet(1.024e+26, 2.4746e7)
def __init__(self, mass, radius):
self.mass = mass # in kilograms
self.radius = radius # in meters
@property
def surfaceGravity(self):
# universal gravitational constant (m3 kg-1 s-2)
G = 6.67300E-11
return G * self.mass / (self.radius * self.radius)
def surfaceWeight(self, otherMass):
return otherMass * self.surfaceGravity
This can't work because the name Planet in the class definition is not
defined.
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