In Lean3, we supported two kinds of local constant:
context-less (inherited from Lean2) and context-based (type,
binder-info and pretty printing name are stored in the context).
The context-less was used in the kernel and a few modules we kept when
we moved from Lean2 to Lean3. Even if we keep the hybrind
representation, we should not expose the context-less to users.
All theorems are proved without using the tactic framework.
Thus, we can define `fin/uint32/uint64` types and their operations
before we define the tactic framework.
Now, `cmp` is just a fixed helper function.
In the future, we will be able to use (more efficient) specialized
versions during code generation by defining simp rules.
We need this feature for:
1) Defining nonlinear search patterns. Example: (?m <= ?m + 1)
2) Preprocessing recursive equations and support the pattern
refinement approach used in Agda. Example: in Agda, they accept
```
def append {A : Type} : Π (m n : nat), Vec A m -> Vec A n -> Vec A (m + n)
| m n nil ys := ys
| m n (cons m' x xs) ys := cons x (append m' n xs ys)
```
These equations have to be refined. For example, `m` has to be
replaced with `0` (in the first equation), and `succ m'` in the
second. To implement this kind of refinement, we need to convert
the pattern variables (local constants) into metavariables during
elaboration. Then, the unassigned metavariables become local constants
again. This preprocessing step will fix some of the issues on #1594.
To completely fix#1594, we will need yet another preprocessing step
which will implement "complete transition" used in the equation
compiler before we start elim_match.cpp
See issue #1694.
There is an orthogonal issue. `simp` (and consequently `unfold`) cannot be used to
reduce projections (e.g., `has_add.add`). This issue has been
previously raised by @Armael, but it was not addressed yet.
We want to make sure string users do not depend on the string
implementation. This is the first step.
We need this refactoring *now* to make sure it will not be
super painful to address issue #1175
This commit fixes issue #1631. However, it is not a perfect solution.
This commit improves the predicate that checks whether a definition is
noncomputable or not. This predicate was implemented before we had
a code generator.
We should refactor the code and use the code generator to check
whether a definition is noncomputable or not. Otherwise, we will
keep finding mismatches between the predicate at noncomputable.cpp
and what the code generator implements.
