[dllthomas]

> if you just want your computation to have state and exceptions the difference shouldn’t matter

But... you don't just want that. You almost certainly care whether state changes are discarded when an exception is thrown. I don't claim that the types there are the most obvious or natural way to specify that, but there is a meaningful difference that shouldn't be handwaved away.

[codebje]

The fact that with transformer stacks you can wind up with state changes being discarded on exception if you get the stack arranged in a particular order isn't what I'd call a _feature_ of transformer stacks :-)

If effect A is invoked before effect B, effect A should happen and stay that way: if I update state before an exception is thrown, the update should persist. If I send a network message before an exception is thrown, the network message is still sent. If I launch the nukes before an exception is thrown, the missiles are still flying.

If I want to batch up state updates to only happen together as a unit, I'll use a transaction effect.