On 13 Oct 2025, at 07:58, Marc Nieper-Wißkirchen <xxxxxx@gmail.com> wrote:

> Can you state precisely what you mean by forbidden certain reorderings?

From the compiler’s perspective, ephemeron-key, ephemeron-value, and ephemeron-broken? are non-deterministic procedures. They are, effectively, IO input procedures. It is simply not allowed to re-order them relative to one another, to try to decide what the value of any variable which is assigned to their result is during partial evaluation, etc.

You made the analogy to IO procedures in your example, but (I find) overgeneralize. I am not talking about forbidding re-ordering of all forms which read and write to the store, obviously. I am talking about three specific procedures whose results are interdependent and absolutely cannot be determined at compile time, comparable to sequential reads from a port.

The case of JavaScript is different, and I think they made that decision for different reasons than the one you guess. Namely, the ECMAScript spec authors are very strict about avoiding observable differences between implementations, such as the timing of garbage collections. This is obviously not Scheme’s philosophy. (This was why there was no WeakRef and no FinalizationRegistry in JS for a long time. I remember because it was frustrating writing JS wrappers around Emscriptened C libraries and having no way to free the resources in Emscripten’s linear C memory blob automatically once the JS wrapper object was collected. I was, to say the least, unimpressed by this excuse.)

Daphne