[Haskell-cafe] side effects (Why Haskell is beautiful to thenovice)

[Alexey Muranov]

On 1 sept. 2015, at 07:49, Tobias Dammers <tdammers at gmail.com> wrote:

> Seriously though, the distinction between an *effect* and a *side
> effect* is important, and using the term "side effect" to indicate
> either is just as ambiguous.

Could you give an example of a side effect in programming, please?

Definition from Oxford dictionary:

  side effect -- a secondary, typically undesirable effect of a drug or medical treatment.

Since we are not talking about drugs but about programs, i fail to see any example of a "side effect" in the sense of this definition, other than, possibly, effects of bugs.

Previously my intuitive understanding of "side effects" in the sense of FP was quite clear: any effect that cannon happen if you execute the program in your mind or with pencil and paper, that is any interaction with the real world (think of programs as calculations).

I agree however that it was not clear if getting user input should be called a "side effect", or an oracle, or something else.

See also http://programmers.stackexchange.com/questions/40297/what-is-a-side-effect

Alexey.