This PR introduces an alternative construction for `DecidableEq`
instances that avoids the quadratic overhead of the default
construction.
The usual construction uses a `match` statement that looks at each pair
of constructors, and thus is necessarily quadratic in size. For
inductive data type with dozens of constructors or more, this quickly
becomes slow to process.
The new construction first compares the constructor tags (using the
`.ctorIdx` introduced in #9951), and handles the case of a differing
constructor tag quickly. If the constructor tags match, it uses the
per-constructor-eliminators (#9952) to create a linear-size instance. It
does so by creating a custom “matcher” for a parallel match on the data
types and the `h : x1.ctorIdx = x2.ctorIdx` assumption; this behaves
(and delaborates) like a normal `match` statement, but is implemented in
a bespoke way. This same-constructor-matcher will be useful for
implementing other instances as well.
The new construction produces less efficient code at the moment, so we
use it only for inductive types with 10 or more constructors by default.
The option `deriving.decEq.linear_construction_threshold` can be used to
adjust the threshold; set it to 0 to always use the new construction.
This PR eliminates uses of `intros x y z` (with arguments) and updates
the `intros` docstring to suggest that `intro x y z` should be used
instead. The `intros` tactic is historical, and can be traced all the
way back to Lean 2, when `intro` could only introduce a single
hypothesis. Since 2020, the `intro` tactic has superceded it. The
`intros` tactic (without arguments) is currently still useful.
This PR replaces all usages of `[:]` slice notation in `src` with the
new `[...]` notation in production code, tests and comments. The
underlying implementation of the `Subarray` functions stays the same.
Notation cheat sheet:
* `*...*` is the doubly-unbounded range.
* `*...a` or `*...<a` contains all elements that are less than `a`.
* `*...=a` contains all elements that are less than or equal to `a`.
* `a...*` contains all elements that are greater than or equal to `a`.
* `a...b` or `a...<b` contains all elements that are greater than or
equal to `a` and less than `b`.
* `a...=b` contains all elements that are greater than or equal to `a`
and less than or equal to `b`.
* `a<...*` contains all elements that are greater than `a`.
* `a<...b` or `a<...<b` contains all elements that are greater than `a`
and less than `b`.
* `a<...=b` contains all elements that are greater than `a` and less
than or equal to `b`.
Benchmarks have shown that importing the iterator-backed parts of the
polymorphic slice library in `Init` impacts build performance. This PR
avoids this problem by separating those parts of the library that do not
rely on iterators from those those that do. Whereever the new slice
notation is used, only the iterator-independent files are imported.
This PR moves `ReflBEq` to `Init.Core` and changes `LawfulBEq` to extend
`ReflBEq`.
**BREAKING CHANGES:**
- The `refl` field of `ReflBEq` has been renamed to `rfl` to match
`LawfulBEq`
- `LawfulBEq` extends `ReflBEq`, so in particular `LawfulBEq.rfl` is no
longer valid
This PR makes `take`/`drop`/`extract` available for each of
`List`/`Array`/`Vector`. The simp normal forms differ, however: in
`List`, we simplify `extract` to `take+drop`, while in `Array` and
`Vector` we simplify `take` and `drop` to `extract`. We also provide
`Array/Vector.shrink`, which simplifies to `take`, but is implemented by
repeatedly popping. Verification lemmas for `Array/Vector.extract` to
follow in a subsequent PR.
This adds a number of lemmas for simplification of `Bool` and `Prop`
terms. It pulls lemmas from Mathlib and adds additional lemmas where
confluence or consistency suggested they are needed.
It has been tested against Mathlib using some automated test
infrastructure.
That testing module is not yet included in this PR, but will be included
as part of this.
Note. There are currently some comments saying the origin of the simp
rule. These will be removed prior to merging, but are added to clarify
where the rule came from during review.
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Co-authored-by: Scott Morrison <scott.morrison@gmail.com>
