Random numbers about compiler

[tinco]

randomNumber = Random.inRange 1 10
main = lift (plainText . show) randomNumber

[evancz]

This is another example: http://elm-lang.org/edit/examples/Reactive/Randomize.elm

Does that clarify things?

[tinco]

But.. I have a question about random numbers too.

randomNumber = Random.inRange 1 10
secondRandomNumber = Random.inRange 1 10
thirdRandomNumber = randomNumber

together a b c = (show a) ++ " " ++ (show b) ++ " " ++ (show c)

main = lift plainText $ lift3 together randomNumber secondRandomNumber thirdRandomNumber

This code returns 7 1 7 for me, but shouldn't it return 7 7 7? Is there some magic difference between referring to a signal directly and through a function?

[evancz]

Random.randomize is a non-deterministic signal function, so given the same signal, it will produce different outputs. You can think of (Random.inRange 0 10) as an alias for (Random.randomize 0 10 (constant ())).

I am not sure if this is "bad" behavior, but I think it is okay. It does not have side-effects observable outside of the Elm RTS, so it does not limit any opportunities to prune unused signals.

[drewlesueur]

Thank you