Class RTS_NAME<T>

java.lang.Object

simula.runtime.RTS_NAME<T>

Type Parameters:

T - the type of the parameter

public abstract class RTS_NAME<T>
extends Object

The Abstract Class RTS_NAME are supporting Simula's Name-Parameters.

The basic principle is to establish an object within the calling scope. This object will have two attribute methods; 'get' og 'put' to evaluate and read the value of the actual parameter, or, if legal, to write into it. The following Java-class is used to perform such parameter transmissions:

	 abstract class RTS_NAME {
	 	abstract T get();

	 	void put(T x) {
	 		error("Illegal ...");
	 	}
	 }

Note that we both use abstract Java classes and 'generics' i.e. the actual type is a parameter. Also note that the 'put' method has a default definition producing an error. This enables redefinition of the 'put' method to be dropped for expression as actual parameters.

Suppose the Simula Procedure:

		procedure P(k); name k; integer k; k:=k+1;

It will be translated to something like this Java method:

	 void P(RTS_NAME k) {
	 	k.put(k.get() + 1); // E.g: k=k+1
	 }

In the calling place, in practice in the actual parameter list, we create an object of a specific subclass of RTS_NAME by specifying the Integer type and defining the get and put methods. Eg. If the current parameter is a variable 'q', then the actual parameter will be coded as follows:

	 new RTS_NAME() {
	 	Integer get() {
	 		return (q);
	 	}

	 	void put(Integer x) {
	 		q = (int) x;
	 	}
	 }

However, if the actual parameter is an expression like (j + m * n) then it will be coded as follows:

	 new RTS_NAME() {
	 	Integer get() {
	 		return (j + m * n);
	 	}
	 }

Here we see that the 'put' method is not redefined so that any attempt to assign a new value to this name parameter will result in an error message.

Field Summary

Fields

Modifier and Type	Field	Description
RTS_RTObject	_CUR	The environment in which evaluations of get'parameters will take place.

Constructor Summary

Constructors

Constructor	Description
RTS_NAME()	Construct a RTS_NAME object

Method Summary

Modifier and Type	Method	Description
abstract T	get()	Evaluate and get the value of a name parameter
T	put(T x)	Write back into a name parameter
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

_CUR

public RTS_RTObject _CUR

The environment in which evaluations of get'parameters will take place.

Constructor Details

RTS_NAME

public RTS_NAME()

Construct a RTS_NAME object

Method Details

get

public abstract T get()

Evaluate and get the value of a name parameter

Returns:

the value

put

public T put(T x)

Write back into a name parameter

Parameters:

x - the value to be written

Returns:

the value written

toString

public String toString()

Overrides:

toString in class Object