Well, Yes, If the consumer side consume the result properly (not getting in the way of GC),  a space leak could be avoided.

On Tue, Jun 19, 2018, 9:54 PM Dr.Koster <drkoster@qq.com> wrote:

In general infinite monadic recursion will leak, since the tail position is always >> or >>= instead of your own recursive function

That seems a bit strong. Monadic recursion *can* leak, but it need not. >>= is typically lazy in its second argument, so it can produce structure lazily. Consider the free monad, for example:

data Free f a = Pure a | Wrap (f (Free f a))

instance Functor f => Monad (Free f) where

  Pure a >>= f = f a

  Wrap ff >>= f = Wrap $ fmap (>>= f) ff

See how we can produce Wrap without using f? As long as the base functor isn't too large, this shouldn't leak.

, but under certain situations, e.g. IO without arguments, the compiler will figure there's no need to push new stack frame. But anyway it's better to checkout yourself rather relying on some weak assumptions.

发自我的iPhone

------------------ Original ------------------

From: Никита Фуфаев <kitttoran@gmail.com>

Date: Wed,Jun 20,2018 2:37 AM

To: haskell-cafe <haskell-cafe@haskell.org>

Subject: Re: [Haskell-cafe] Memory leak in infinite recursion

Hello everyone

In C you can't implement main loop with recursion like

void mainLoop() {

  doSomething();

  mainLoop();

}  

because without optimisations stack will overflow.

In haskell it's common to write

mainLoop = doSomething >> mainLoop, and it doesn't leak memory because of haskell's evaluation model.

Does memory leak or argument stack overflow happen in this case?

mainLoop = doSomething >> mainLoop >> exit ExitSuccess

What about this case?

mainLoopModeA = do

  doSomething

  when condition mainLoopModeB

  mainLoopModeA

mainLoopModeB = do

  doSomethingElse

  when anotherCondition mainLoopModeA

  mainLoopModeB

or this case?

mainLoopModeA = do

  doSomething

  if condition

    then mainLoopModeB

    else mainLoopModeA

mainLoopModeB = do

  doSomethingElse

  if anotherCondition 

    then mainLoopModeA

    else mainLoopModeB

--

Nikita Fufaev

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