ocaml vs haskell

Haskell:
[(a,b,c)|a<-[1..n],b<-[a..n],c<-[b..n],a+b+c==n]

Ocaml:
?

The set of all tuples (a,b,c), a,b,c integer, such that a is between 1 and n, b is between a and n, and c is between b and n, and a+b+c is equal to n.  Nope, not a single real-life use.

how to write it in ocaml then

Using a syntax extension from Batteries:

[? List: (a, b, c) | a <- 1--n; b <- a--n ; c <- b--n; a + b + c = n ?]