[lang][grammar] Default value for function parameters

[gallandarakhneorg]

It may be useful to specify default values for the parameters:

def myAction(String a, int b=35) {
}

[srodriguez]

Steph, that's a great idea. However, should capacity definition allow default values?
For agent or behavior actions, it would be clear.

[gallandarakhneorg]

Yes, I guess.
It may be very helpful for the capacity caller to have default values.

We may discuss on the default parameters in Skills.
I have in my mind the default value in the C++.
Let the Capacity is analog to the declaration in the header, and the Skill is analog to the definition in the code file. It is common to define the default values in the header file and not in the code file.
Consequently, the best practice is to define the default values in the Capacity, and not in the Skill.
Is it possible to generate a compilation error when a default value is written in the Skill?

[gallandarakhneorg]

I propose the following syntax:

def myAction1(a : String, b : int = 35) { CODE1 }
def myAction2(a : String, b : int = 35, c : char) { CODE2 }

The generated Java functions will be:

public void myAction1(String a, int b) { CODE1 }
public void myAction1(String a) { myAction1(a, 35); }
public void myAction2(String a, int b, char c) { CODE2 }
public void myAction2(String a, char c) { myAction2(a, 35, c); }

[gallandarakhneorg]

Let the following code with ambiguity:

def myAction(a : char, b : int = 1, c : int = 2, d : char) { }

The generated Java code may be:

public void myAction(char a, int b, int c, char d) { }
public void myAction(char a, int b, char d) { myAction(a,b,2,d); }
public void myAction(char a, char d) { myAction(a,1,2,d); }

[gallandarakhneorg]

Since we are using Xtext 2.6, (issue #93), the jvm inferrer and the validator are not working any more.