FuncPtrs/Templates (I'm way over my head!)

Using Arduino Programming Questions
1

I'm way over my head here.... But trying to piece this together mostly to see if it's even possible, and to help myself learn about function pointers and templates. I just about understand the examples I've got working but I'm over-reaching for sure.

So...

This example of a function pointer works:

////// Function Pointer Test
void (*btnFuncPtr)(void);
void execute(){ btnFuncPtr(); }
void Test1() { Serial.println("Test 1 Worked"); }
void setup() { Serial.begin(9600); }

void loop() {
  btnFuncPtr = &Test1;
  execute();
  while(1);
}

But I can only hook in a void function that takes no parameters.

This example of a template that takes any number of arguments (of any types) works:

/////// Multiple Argument Test
template <typename T>
void func(T t) { Serial.println(t); }

template<typename T, typename... Args>
void func(T t, Args... args) {
    Serial.println(t);
    func(args...) ;
}

void setup() { Serial.begin(9600); }

void loop() {
  func(1, "This is", 6.9f, "A", "Test");
while(1);
}

For no reason other than my own amusement and learning I'm trying to combine the two.
So I can essentially have a function pointer to any function, no matter what or how many arguments are required.

Can it be done?

2

What is the purpose of a template function if no specific type is required for it?

Guess you have already found this.

3

That is the beauty and the horror of C. Yes. You can do almost anything.

4

The goal is to have the function pointer point to any function, no matter what or how many arguments are required. Is the template not even needed for this?

I did see that, yes! Although it's just as much over my head. Maybe the answer is in there but I do not see it yet. (Plenty of studying left to do)

5

Then what?

6

Haven't decided yet. Just exploring to see what's possible. The thought process started because I gave my button class function pointers to call when pressed. Which is fine for void functions with no parameters but I thought 'what if I wanted to hook in other functions that looked a little or very different'. Sure you could probably write a million overloads. But maybe templates are the answer. Who knows!

7

you can define function ptrs to functions with a specified set of arguments. it's common to specify a void* argument which can then be cast to the type needed by the function

see variadic functions for functions with a variable # of arguments.

8

Those are nicknamed, "callback" functions. As they don't expect to return any values, they also don't accept any parameters. That makes them a lot safer than calling void function pointers from a main program, and/or passing parameters with them. They're normally just event handlers.

9

This was more of a 'can it be done' than a 'should it be done' really.

But if it can be done, I can't suss it :joy:

10

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