# Changelog (unreleased)

To avoid having old PRs put changes into the wrong section of the CHANGELOG,
new entries now go to the present file as discussed
[here](https://github.com/math-comp/math-comp/wiki/Agenda-of-the-April-23rd-2019-meeting-9h30-to-12h30#avoiding-issues-with-changelog).

The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).

## [Unreleased]

### Added

- in `bigop.v`, added lemma `sumnB`.

- in `seq.v`,
  + new higher-order predicate `pairwise r xs` which asserts that the relation
    `r` holds for any i-th and j-th element of `xs` such that i < j.
  + new lemmas `allrel_mask(l|r)`, `allrel_filter(l|r)`, `sub(_in)_allrel`,
    `pairwise_cons`, `pairwise_cat`, `pairwise_rcons`, `pairwise2`,
    `pairwise_mask`, `pairwise_filter`, `pairwiseP`, `pairwise_all2rel`,
    `sub(_in)_pairwise`, `eq(_in)_pairwise`, `pairwise_map`, `subseq_pairwise`,
    `uniq_pairwise`, `pairwise_uniq`, and `pairwise_eq`.
  + new lemmas `zip_map`, `eqseq_all`, and `eq_map_all`.

- in `path.v`, new lemmas: `sorted_pairwise(_in)`, `path_pairwise(_in)`,
  `cycle_all2rel(_in)`, `pairwise_sort`, and `sort_pairwise_stable`.

- in `interval.v`, new lemmas: `ge_pinfty`, `le_ninfty`, `gt_pinfty`, `lt_ninfty`.

- in `order.v`
  + we provide a canonical total order on ordinals and lemmas
    `leEord`, `ltEord`, `botEord`, and `topEord` to translate generic
    symbols to the concrete ones. Because of a shortcoming of the
    current interface, which requires `finOrderType` structures to be
    nonempty, the `finOrderType` is only defined for ordinal which are
    manifestly nonempty (i.e. `'I_n.+1`).
  + new notation `Order.enum A` for `sort <=%O (enum A)`, with new
    lemmas in module `Order`: `cardE`, `mem_enum`, `enum_uniq`,
    `cardT`, `enumT`, `enum0`, `enum1`, `eq_enum`, `eq_cardT`,
    `set_enum`, `enum_set0`, `enum_setT`, `enum_set1`, `enum_ord`,
    `val_enum_ord`, `size_enum_ord`, `nth_enum_ord`, `nth_ord_enum`,
    `index_enum_ord`, `mono_sorted_enum`, and `mono_unique`.
  + a new module `Order.EnumVal` (which can be imported locally), with
    definitions `enum_rank_in`, `enum_rank`, `enum_val` on a finite
    partially ordered type `T`, which are the same as the one from
    `fintype.v`, except they are monotonous when `Order.le T` is
    total. We provide the following lemmas: `enum_valP`,
    `enum_val_nth`, `nth_enum_rank_in`, `nth_enum_rank`,
    `enum_rankK_in`, `enum_rankK`, `enum_valK_in`, `enum_valK`,
    `enum_rank_inj`, `enum_val_inj`, `enum_val_bij_in`,
    `eq_enum_rank_in`, `enum_rank_in_inj`, `enum_rank_bij`,
    `enum_val_bij`, `le_enum_val`, `le_enum_rank_in`, and
    `le_enum_rank`.  They are all accessible via module `Order` if one
    chooses not to import `Order.EnumVal`.
### Changed

- In `ssralg.v` and `ssrint.v`, the nullary ring notations `-%R`, `+%R`, `*%R`,
  `*:%R`, and `*~%R` are now declared in `fun_scope`.

- across the library, the deprecation mechanism to use has been changed from the
  `deprecate` notation to the `deprecated` attribute (cf. Removed section).

### Renamed

- in `path.v`,
  + `sub_(path|cycle|sorted)_in` -> `sub_in_(path|cycle|sorted)`
  + `eq_(path|cycle)_in` -> `eq_in_(path|cycle)`

### Removed

- in `ssreflect.v`, the `deprecate` notation has been deprecated. Use the
  `deprecated` attribute instead (cf. Changed section).

- in `seq.v`, `iota_add` has been deprecated. Use `iotaD` instead.

- in `ssrnat.v` and `ssrnum.v`, deprecation aliases and the `mc_1_10`
  compatibility modules introduced in MathComp 1.11+beta1 have been removed.

- in `seq.v`, remove the following deprecation aliases introduced in MathComp
  1.9.0: `perm_eq_rev`, `perm_eq_flatten`, `perm_eq_all`, `perm_eq_small`,
  `perm_eq_nilP`, `perm_eq_consP`, `leq_size_perm`, `uniq_perm_eq`,
  `perm_eq_iotaP`, and `perm_undup_count`.

### Infrastructure

### Misc