>    I'm using Ocaml for an interval arithmetic application.  I"m
> curious about
> what the Ocaml parser/compiler does to float constants.  May I assume
> that for any constant I enter, eg. 3.1415... (for N digits of pi), that
> the compiler will give me a closest machine representable number?
> i.e., if I bound a constant by the previous and next floating point
> value to
> that given me by the compiler,
> will it always be the case that my original (mathematical) constant
> lies in that interval?

For the concrete exemple of PI, perhaps you could use a mathematical 
calculation to get its best value:

# 4. *. atan 1. ;;
- : float = 3.14159265358979312
(but the last number '2' is wrong)

For other constants, maybe there are equivalent things?