Since println is just an example, perhaps it isn't really a good example to use when trying to give an example of how impure functions can have side effects. Sending some ink to a printer or altering pixels on a screen isn't exactly a compelloing argument for side effects.
Maybe a better example function is one that deletes data from your hard drive, or sens control signals to a robot that locks the doors or changes the A/C or starts some industrial process, releasing toxic chemicals.
The point is println does have a side effect, it's just not a very interesting one.
Or maybe the definition of side effect is what is causing the problem, after all - executing any function does have physical side effects - electrons move, electromagnetic styate chabnes, ambient temperature changes. Maybe the problem is where we draw the line for observable side effects.
Comments
Since println is just an example, perhaps it isn't really a good example to use when trying to give an example of how impure functions can have side effects. Sending some ink to a printer or altering pixels on a screen isn't exactly a compelloing argument for side effects.
Maybe a better example function is one that deletes data from your hard drive, or sens control signals to a robot that locks the doors or changes the A/C or starts some industrial process, releasing toxic chemicals.
The point is println does have a side effect, it's just not a very interesting one.
Or maybe the definition of side effect is what is causing the problem, after all - executing any function does have physical side effects - electrons move, electromagnetic styate chabnes, ambient temperature changes. Maybe the problem is where we draw the line for observable side effects.