5 ms·

idempotent -> side-effect-free? safely-repeatable?

by chrisweekly 6y ago

tyingq 6y ago
Ah, that's helpful. "Safely repeatable, with no side effects" will be my new answer if anyone asks.
- chrisweekly 6y ago
  Well, per others' responses the "no side effects" part is not quite accurate. The definition in plain English is actually pretty simple: idempotency = "has the same effect, no matter how many times it's run". Like a dedicated "Power On" button (vs a "power toggle" button).
marcosdumay 6y ago
> side-effect-free Hum... No, that's not the meaning at all. > safely-repeatable And now you'll get stuck explaining exactly what "safe" means.
jolmg 6y ago
> side-effect-free? No, those are pure. A pure, idempotent function would be one where f(f(x)) = f(x). An idempotent function could have side-effects. Imagine turn_on() where if it's already on, then nothing happens and it just stays on.
- tyingq 6y ago
  I think there's two different readings of "side effect free" here. The fact that nothing happens on the second+ invocation is, for me, the example of no unwanted side effects. An unwanted side effect might be sending more voltage down the line on each invocation...120, 240, 360.
  - jolmg 6y ago
    Side-effect is a very well-established term, though[1]: > In computer science, an operation, function or expression is said to have a side effect if it modifies some state variable value(s) outside its local environment, that is to say has an observable effect besides returning a value (the main effect) to the invoker of the operation. > The fact that nothing happens on the second+ invocation is, for me, the example of no unwanted side effects. I don't think you'll ever find a definition that says something about second invocations. [1] https://en.wikipedia.org/wiki/Side_effect_(computer_science) https://en.wikipedia.org/wiki/Side_effect_(computer_science)
- chrisweekly 6y ago
  Quite right. How about "same-result-returning"?
  - jolmg 6y ago
    "same-result-returning" sounds like pure functions which return the same result when given the same arguments. I prefer entropicdrifter's "one-and-done".

idempotent -> side-effect-free? safely-repeatable?

tyingq 6y ago

Ah, that's helpful. "Safely repeatable, with no side effects" will be my new answer if anyone asks.

chrisweekly 6y ago
Well, per others' responses the "no side effects" part is not quite accurate. The definition in plain English is actually pretty simple: idempotency = "has the same effect, no matter how many times it's run". Like a dedicated "Power On" button (vs a "power toggle" button).

marcosdumay 6y ago

> side-effect-free Hum... No, that's not the meaning at all. > safely-repeatable And now you'll get stuck explaining exactly what "safe" means.

jolmg 6y ago

> side-effect-free? No, those are pure. A pure, idempotent function would be one where f(f(x)) = f(x). An idempotent function could have side-effects. Imagine turn_on() where if it's already on, then nothing happens and it just stays on.

tyingq 6y ago
I think there's two different readings of "side effect free" here. The fact that nothing happens on the second+ invocation is, for me, the example of no unwanted side effects. An unwanted side effect might be sending more voltage down the line on each invocation...120, 240, 360.
- jolmg 6y ago
  Side-effect is a very well-established term, though[1]: > In computer science, an operation, function or expression is said to have a side effect if it modifies some state variable value(s) outside its local environment, that is to say has an observable effect besides returning a value (the main effect) to the invoker of the operation. > The fact that nothing happens on the second+ invocation is, for me, the example of no unwanted side effects. I don't think you'll ever find a definition that says something about second invocations. [1] https://en.wikipedia.org/wiki/Side_effect_(computer_science) https://en.wikipedia.org/wiki/Side_effect_(computer_science)
chrisweekly 6y ago
Quite right. How about "same-result-returning"?
- jolmg 6y ago
  "same-result-returning" sounds like pure functions which return the same result when given the same arguments. I prefer entropicdrifter's "one-and-done".