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"Yeah, no, you are redefining factorial in terms of different `pred` functions, and I'm simply defining `prev` without redefining factorial." No, you are not s

"Yeah, no, you are redefining factorial in terms of different `pred` functions, and I'm simply defining `prev` without redefining factorial." No, you are not simply defining `prev`, you are creating a new class using `computer` as a base and supplying all its methods with the new definition of `prev`. Let me complete your example: class computer = object(self) method factorial x = if x = 0 then 1 else x * self#factorial (self#pred x) method pred x = x - 1 end class computer_enhanced = object inherit computer method pred x = x end obj_computer = new computer obj_computer.factorial(5) //still works obj_computer_enhanced = new computer_enhanced obj_computer_enhanced.factorial(5) //stack overflow And the same with my example: let rec fact(x, prev) = if x <= 1 then 1 else x * fact(prev(x), prev);; let factorial(x) = fact(x, fun x -> x-1);; let enhanced_factorial(x) = fact(x, fun x -> x);; factorial(5);; (*works*) enhanced_factorial(5);; (*stack overflow*) In both cases the old `factorial` works and the enhanced one fails.

ernst_klim 7y ago
> In both cases the old `factorial` works and the enhanced one fails. Does class computer_enhanced = object inherit computer method prev x = x end tells you that factorial definition changed and that it's dependent on prev? No. Does fact(x, fun x -> x) tells you that this function's behavior depends on `fun x -> x`? Yes.
- protomolecule 7y ago
  `factorial` definition hasn't changed, what changed is its implicit parameter. The word 'inherit' tells you that all methods of the `computer` class are potentially affected, including `factorial` unless you can see in `pred`'s contract that it affects only `factorial`. If you call your class `computer` and put a bunch of unrelated methods in it, then, yes, you are in big trouble, but you can abuse anything - you can create a data structure with hundreds of data members and make all your 'pure' functions take and return it. To sum it up: I see your point, but I don't think that it's a fatal flow of OOP, it's just a way to abuse it.

ernst_klim 7y ago

> In both cases the old `factorial` works and the enhanced one fails. Does class computer_enhanced = object inherit computer method prev x = x end tells you that factorial definition changed and that it's dependent on prev? No. Does fact(x, fun x -> x) tells you that this function's behavior depends on `fun x -> x`? Yes.

protomolecule 7y ago
`factorial` definition hasn't changed, what changed is its implicit parameter. The word 'inherit' tells you that all methods of the `computer` class are potentially affected, including `factorial` unless you can see in `pred`'s contract that it affects only `factorial`. If you call your class `computer` and put a bunch of unrelated methods in it, then, yes, you are in big trouble, but you can abuse anything - you can create a data structure with hundreds of data members and make all your 'pure' functions take and return it. To sum it up: I see your point, but I don't think that it's a fatal flow of OOP, it's just a way to abuse it.