[Haskell-beginners] Why does Haskell PVP have two values for the major version? "A.B..." and a couple other questions

[Zach Moazeni]

Oh! I sent this to the Beginner list because it feels Beginner-ish (at
least to me, who might be missing something obvious). But if this is more
appropriate for Cafe, someone please let me know and I'll email that list
instead.

On Mon, Dec 15, 2014 at 7:38 PM, Zach Moazeni <zach.lists at gmail.com> wrote:
>
> Hello,
>
> Forgive me if this is a frequently asked question, I've searched the web
> and can't find an answer.
>
> What is the history that led up to the PVP
> <https://www.haskell.org/haskellwiki/Package_versioning_policy>
> specifying two values as the major version?
>
> I come from other tools that primarily use http://semver.org/ (or a
> variant) and I'm confused in what cases I should bump "A" but not "B" (or
> bump "B" but not "A")?
>
> A concrete example: If I make backwards incompatible changes to a package
> whose latest version is 1.0.x, should the next version be 2.0.x or 1.1.x?
> What sorts of things should I consider for choosing 2.0 over 1.1 and vice
> versa?
>
>
> Another question, by far most packages I have encountered either lead with
> a 0 or a 1 for "A". Does that have some bearing on the long term stability
> that package users should expect in the future?
>
> Finally, if "1.0.x.." is meant to convey a level of long term support,
> does "B" get rarely used? Since "C" version bumps to include backwards
> compatible additions, and "D"+ for backwards compatible bug fixes. (I know
> "D" isn't technically a PVP category, I'm just relating it to the patch
> version of semver).
>
> Thanks for your help!
> -Zach
>
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