[anuragsoni]

> You are correct that Ocaml has a ref type (though I believe it is actually a special case of a mutable record with one field). > There is a small difference between an immutable record of which one property is a reference to changing data and a mutable record where the record itself changes. I prefer the first though I realize this is mostly preference.

In OCaml ref is defined as

  type nonrec 'a ref = 'a ref = { mutable contents : 'a }

so it is an immutable record which contains one item which is mutable.

> In any case, the idea of outright changing a formerly mutable structure to an immutable one would be unthinkable in most languages due to all the breakages it is likely to cause.

I agree with you. I started using OCaml in 2018 but I believe many linux distributions stayed on OCaml 4.05 (the release before safe-string was default) for a while because of breakages.