Define and call

The way of define function in MCFPP has some differences with C/Java, and more similar to the grammar of Python.

Function definition

In MCFPP, the grammar of define a function is shown below:

func functionName(parameter1, parameter2, ...) -> returnType{
    #Function body
}

func is the keyword of function, while functionName is the identifier of the function. The following parameter1, parameter2, ... is the parameter list of the function. returnType is optional, which is the returned type of the function. Function body is a series of statements surrounded by {}. Here's a example below:

func add(int a, int b) -> int{
    return a + b;
}

The name of the function is add, it have two integer-type parameters a and b, return value is also integer type. Its function is add the two parameters and return them.

return

return is same as the return command in Minecraft, both used to return the returned value of the function. It's grammar is return expression;, expression is an expression, it's value is the returned value of the function.

If a function defined the type of the returned value, then each branch of it must have return statement, so the function must would return a value. And the value that return statement returned must have the same type as the type of return value of the function, or the subtype of the returned value's type.

If a function haven't defined the return value's type, then the default is void, which won't return any value. Now, return statement is still available, but its grammar becomes return;, without any expression. It will stop the function immediately.

Call the function

In MCFPP, grammar of call function is the same as in C/Java, that's functionName(parameter1, parameter2, ...);. In it, the functionName is the name of function,parameter1, parameter2, ... are the parameters to the function, here's the example:

func test(){
    print(add(1, 2));  #the add function defined before 
}

In this example, test function called add function, and sent two parameters 1 and 2. add function returns 3, so the test function will print 3.

The argument of function

In the function, the change to the parameter won't affect the variables out of the function. For example:

func test(int a){
    a = 5;
}

void main(){
    int a = 0;
    test(a);
    print(a);   #output 0
}

In this case, test function modified the passed in parameter a, but the a in main function haven't been affected.