`simp only` will not apply this simproc anymore. Users must now write
`simp only [reduceCtorEq]`. See RFC #5046 for motivation.
This PR also renames simproc to `reduceCtorEq`.
close#5046
@semorrison A few `simp only ...` tactics will probably break in
Mathlib. Fix: include `reduceCtorEq`.
Remark: when splitting an `if-then-else` term, the subgoals now have
tags `isTrue` and `isFalse` instead of `inl` and `inr`.
closes#4313
---------
Co-authored-by: Mario Carneiro <di.gama@gmail.com>
This makes changes to the definitions of Associativity, Commutativity,
Idempotence and Identity classes to be more aligned with Mathlib's
versions.
The changes are:
* Move classes are moved from `Lean` to root namespace.
* Drop `Is` prefix from names.
* Rename `IsNeutral` to `LawfulIdentity` and add Left and Right
subclasses.
* Change neutral/identity element to outParam.
* Introduce `HasIdentity` for operations not intended for proofs to
implement
The identity changes are to make this compatible with
[Mathlib](718042db9d/Mathlib/Init/Algebra/Classes.lean)
and to enable nicer fold operations in Std that can use type classes to
infer the identity/initial element on binary operations.
---------
Co-authored-by: Kyle Miller <kmill31415@gmail.com>
