| > ...I consider OCaml's mutable strings a far worse design error.
| 
| That's interesting. Why?

Because it destroys persistence, one of the most fundamental advantages
of functional programming. Any function I call with a string argument
can
choose to modify it, and cause side-effects elsewhere.

Even Java has immutable strings, doesn't it? And I notice this feature
of OCaml is fixed in F#. All for very sound reasons, in my opinion.

John.