Newbie question: OCaml equivalent of Haskell's show?

["Antony Courtney" <antony.courtney@gmail.com>]

I'm an experienced Haskell hacker trying OCaml for the first time.

One thing I am desperately searching for but have been unable to find
is some direct runtime access to the string representation of
arbitrary OCaml values.  I have written a little option pricer that
constructs a
   float option array array
in a function.  I've got a little buglet in my function so I'd like to
print the intermediate states of this value from inside the function.
How do I do that, short of writing my own recursive pretty printer /
formatter?  An OCaml form of the Haskell Show type class would be
great, but a hack to provide programmatic access to the polymorphic
pretty printer that obviously already exists in the OCaml toplevel
would be fine.

I've scoured the standard library docs, manual, tutorials and a few
books, looked at the FAQ and am amazed that I haven't found the answer
to this.  I am hopefully just missing something obvious; would be
grateful if someone could point me towards the answer!

Apologies if this belongs on ocaml-beginners.

Thanks,

     -Antony