I am looking for an efficient representation of binary relations in 
OCaml. I have used bitvectors in the past but would like to use a more 
high-level and less imperative data structure.

The most important operation is the following. For a binary relation R 
over \X x \Y compute for a set X the set X' = { y | (x,y) in  R for all 
x in X}. In other words, X' is the set of y that are common to all x in 
X. Likewise, Y' must be computed. This operation requires to compute 
the intersection of sets and was the main reason I chose bitvectors. If 
you know about a suitable data structure I would glad to hear about it.

-- Christian

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http://www.st.cs.uni-sb.de/~lindig/