public class MyFunction extends AbstractFunction<Double> {
public static final SDFDatatype[][] accTypes = new SDFDatatype[][] {{ SDFDatatype.DOUBLE },
{ SDFDatatype.DOUBLE }};
@Override
public String getSymbol() {
return "myFunction";
}
@Override
public Double getValue() {
double a = (double) this.getInputValue(0);
double b = this.getNumericalInputValue(1);
return a +b;
}
@Override
public SDFDatatype getReturnType() {
return SDFDatatype.DOUBLE;
}
@Override
public int getArity() {
return 2;
}
@Override
public SDFDatatype[] getAcceptedTypes(int argPos) {
if (argPos < 0) {
throw new IllegalArgumentException(
"negative argument index not allowed");
}
if (argPos > this.getArity()) {
throw new IllegalArgumentException(this.getSymbol() + " has only " + this.getArity() + " arguments: Two double values.");
}
return accTypes[argPos];
}
}
Access to function attributes
To Access the attributes of the function you can use the getInputValue or the getNumericalInputValue methods. While the first method returns an object, the second already cast the input value to a double value. Both methods takes the position index of the attribute as an argument. The datatype of the accepted attributes is set in the getAcceptedTypes function. Thus, a MEP function can handle multiple data types for each attribute. The total number of attributes is set in the getArity method. The last required method is the getSymbol method that sets the name of the function as used in an expression in a processing query.
Access to meta attributes
To access the meta attributes of an incoming streaming object you can use the getMetaAttribute function.
Access to additional content
To access the additional content of an incoming streaming object you can use the getAdditionalContents method to access all contents. If you only want to access a special field you can issue the getAdditionalContent(fieldName) method.