Question

Is message passing taking place when calling a function with no input?

i.e. with: object.toString();

Am I passing a message to ‘object’?

This might vary between languages, but I’m specifically referring to Java.

Answer 1

yes and no … message passing is a model … the only languages i personally know, that actually employ these semantics are Smalltalk and Objective-C … so yes, in the sense that object.method() is as much message passing as object.method(param_1,param_2,...param_n) … and no, because object.method(param_1,param_2,...param_n) means:

1. lookup the function pointer for method in object
2. invoke that function passing object as well as param_1,...,param_n to it

this absolutely captures the semantics of message passing, but in the end, this is simple function invocation as you know it from procedural programming … the number of parameters neither changes the semantics of the model, nor the implementation … the parameter list for the actual call simply contains only object …