Does it reorder? I would expect these two to be equivalent
>
>     let x = f (g 1) (h ()) in
>
> and
>
>     let f2 = f (g 1) in
>     let x = f (h ()) in
>
> and in the second case the order is clearly g before h.
>

It depends on the order of evaluation. I forgot to specify that I was
taking right to left here (the order of evaluation is unspecified in Ocaml,
if I remember correctly).


> If the order is indeed to evaluate the last argument first then
>
>     let t1 = h () in
>     let t2 = g 1 in
>     let x = f t2 t1 in
>     let y = t2 in
>     x + y
>
> It's not hard to preserve the order whatever it may be.
>

Yes, it is what I meant by "monadic form". To sum up, I'd say exceptions
have some interesting properties, but are quite far from pure function as
far as optimisation opportunities are concerned.