Move infix comparison operators in submodule

[bschommer]

Since it can become quite annoying if the generic comparison operators are shadowed. As said in #20 (comment) I tried to update some code using Zarith and ended up having to change a lot of code in order to get it compiling again.

I think it is more save to hide these infix operators in a submodule, which still allows the shorter usage but avoids problems when the module Z or Q are opened or included.

[hhugo]

Is this not going to happen ?

[bschommer]

As I understood @antoinemine he was not in favor of changing this, see #20 (comment).

[antoinemine]

To be fair, the strongest argument for keeping <, <=, etc. in the module (instead of a submodule) is for Q, not Z. In Q, using the polymorphic operators result in hard-to-discover bugs. I'd like something like "Q.(a + b < c)" to do the right thing by default. I'm also happy with having an error when using < for non-Q objects after a "open Q" or "include Q" : this means the I'm mixing the polymorphic operators with the monomorphic ones. Hiding the operators in a submodule of Q would defeat the purpose.
For Z, there is one less reason to do this as the polymorphic operators work as well as the monomorphic ones. And I'm wary of compatibility issues when people start using 1.8 and have errors such as @bschommer, compounded with the fact that Z start to differ from Int32 and Int64's API.
So, should we include the operators directly in Q and not in Z (at the cost of some inelegance difference between Z and Q's API) ?

[bschommer]

I would be fine with just adding a submodule for Z and keeping Q as it is, sorry if I closed this too fast and misunderstood the comment. What would be interesting is how many opam packages break with the version from version 1.8

[bschommer]

I updated the PR to only move the z variants of the comparison operators in a submodule.

[bschommer]

Thanks.