@Override
    protected boolean onExecute() {
        for (int i = 0; i < getNumArgs(); i++) {
            getArg(i).execute();
            ((StringResultNode)getResult()).append(getArg(i).getResult());
        }
        return true;
    }
This function is an instruction to concatenate the bits of all arguments in order.

@author baldersheim
@author Simon Thoresen Hult
searchlib/src/main/java/com/yahoo/searchlib/expression/StrCatFunctionNode.java