Is it the normal behavior for group_by?

[c-cube]

Is it the normal behavior for group_by?

[grayswandyr]

Got it!
I should have written:

utop # let s4 = S.group_by ~hash:(fun (a, _) -> String.hash a) 
~eq:(fun (a1, _) (b1, _) -> String.equal a1 b1) s;;
val s4 : (string * string) list S.t = <fun>
utop # print2 s4;;
[("a", "f"), ("a", "e"), ("a", "d")]
[("b", "f"), ("b", "e"), ("b", "d")]
[("c", "f"), ("c", "e"),
("c", "d")]
- : unit = ()

So it was not clear for me, from the documentation, what the hash function had to do... Perhaps the doc should be updated here, but I don't really know how to formulate this...

[c-cube]

Ok, I see. The invariant you were missing is quite classic: eq x y ==> hash x = hash y. In this particular case it would not hold.

[c-cube]

I added the invariant to the docs,thanks. Release incoming.