[#211] Safer maximum and stuff

Martoon-00 commented 4 years ago

Description

Get rid of unsafe maximum, foldr1, and similar functions. Did it in the same way as done for head:

Container typeclass now has safeMinimum :: t -> Maybe (Element t).
Additionally we provide minimum :: NonEmpty a -> a.
Plus the original unsafe version put to Unsafe module.

One thing which worries me is that now one cannot simply write something like foldr1 (+) [1..5]. Constructing NonEmpty manually is not pleasant,OverloadedLists extension is rarely used because it would break many other function calls, e.g. forM [1..5]. Not sure which solution is best here.

Related issues(s)

Fixes #211.

✓ Checklist for your Pull Request

Ideally a PR has all of the checkmarks set.

If something in this list is irrelevant to your PR, you should still set this checkmark indicating that you are sure it is dealt with (be that by irrelevance).

[x] I made sure my PR addresses a single concern, or multiple concerns which are inextricably linked. Otherwise I should open multiple PR's.
[x] If your PR fixes/relates to an open issue then the description should reference this issue. See also auto linking on github.

Related changes (conditional)

Tests
- [x] If I added new functionality, I added tests covering it.
- [x] If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
Documentation

I checked whether I should update the docs and did so if necessary:
- [x] README
- [x] Haddock
Record your changes
- [x] I added an entry to the changelog if my changes are visible to the users and
- [x] provided a migration guide for breaking changes if possible

Stylistic guide (mandatory)

[x] My commit history is clean (only contains changes relating to my issue/pull request and no reverted-my-earlier-commit changes) and commit messages start with identifiers of related issues in square brackets.

Example: [#42] Short commit description

If necessary both of these can be achieved even after the commits have been made/pushed using rebase and squash.

Martoon-00 commented 4 years ago

Note that doctest currently fails.

Mda. I guess having examples there is not so important? Too lazy to add a function which would make use of (+).

gromakovsky commented 4 years ago

I think it's not so important, but apparently you just need to add a corresponding import to the comment starting with $setup above.

Martoon-00 commented 4 years ago

Wow, that's magic. Now I see why this $setup is needed.

serokell / universum