public class NullToken extends Token
NullTokens are not part of the Ptolemy II type lattice. As such, a NullToken will violate type resolution if passed through a typed IO port. For this reason, Null Tokens are placed directly into receivers without using the send() method of TypedIOPort. This tactic circumvents type resolution constraints and affirms the notion that NullTokens do not represent computation and hence should never be incorporated into actor code. Note further, that the get() method of DDEReceiver does not return NullTokens but instead consumes them and then proceeds until a "real" token becomes available.
|Constructor and Description|
add, addReverse, divide, divideReverse, getType, isCloseTo, isCloseTo, isEqualTo, isNil, modulo, moduloReverse, multiply, multiplyReverse, notSupportedConversionMessage, notSupportedIncomparableConversionMessage, notSupportedIncomparableMessage, notSupportedMessage, notSupportedNullNilStringMessage, one, pow, subtract, subtractReverse, toString, zero, zeroReturnType