@kha This commit fixes the bug we discussed on slack.
I had to repair one of the tests. The broken test made me
realize that if we use the unbundled approach to define something like
`is_semiring`
```
class is_semiring (α : Type) (plus : α → α → α) (mul : α → α → α) (zero : out_param α) (one : out_param α) :=
...
```
Then, to retrieve a `is_semiring` instance, we need to know `α`, `plus`
and `mul`. This is problematic because we may be in a context where one
of them cannot be inferred. This would force user to manually provide
the missing (input) parameter. We are not considering the unbundled
approach for complex algebraic structures such as `semiring`, `ring` and
`field`, but I wanted to document this limitation here since we may face
it in other type classes.
I think it is a bad idea to add back `inout_param` and have both:
`inout_param` and `out_param`. The previous `inout_param` created
many instabilities and hard to diagnose failures.
- An new simp attribute may depend on other existing attributes
- Add `[norm]` simp attribute. It is an extension of the default `[simp]` attribute.
It should be used to add extra rules for normalizing goals.
These extra rules are used to produce normal forms and/or reduce the
number of constants used in a goal. Here is an example coming from a
discussion with @kha. When working with monads, we may want to
eliminate `<$>` by using the lemma `f <$> x = x >>= pure ∘ f`.
This lemma is in the `[norm]` simp set, but it is not in `[simp]`
@kha I've added
iterator.extract : iterator -> iterator -> option string
It returns `none` if the iterators are "incompatible".
If this function is inconvenient to use, we can change it and return the
empty string in these cases.
Given iterators `it1` and `it2`, if they are sharing the same string
object in memory, then the cost is O(pos(it2) - pos(it1)).
If not, we have an extra O(N) step where we check whether the strings
being iterated by it1 and it2 are equal (`N` is the size of the strings).
In most applications, I believe the iterators will share the string
object.
I didn't test the code much. BTW, I found an unrelated bug at
vm_string.cpp. So, I'm not very confident this code is rock solid.
This command is not just a cosmetic feature.
We need it to defined `id_rhs` before the tactic framework is defined.
We want `id_rhs` to be used in all definitions generated by the equation
compiler. Right now, it is only used in definitions defined after the
tactic framework.
On OSX, Lean was often crashing when using trace messages.
I identified a problem in the thread finalization process.
In OSX, the `silent_ios_helper` at `library/trace.cpp` was being
finalized after the `null_streambuf` at `util/null_ostream.cpp`.
There was also a memory corruption problem also related to
`null_streambuf`.
This commit fixes this problem by using the following recipe
for creating null output stream buffers in C++.
https://stackoverflow.com/questions/11826554/standard-no-op-output-stream
It fixes the issue by propagating the correct information to the
equation compiler.
The fix may be a little bit hackish, but it is comapatible with
the approach we are already using: store `m_is_meta` flag in the equation
macro.
Disclaimer: we may still have other instances of this bug, since
the information may still be propagated incorrectly in other places.
I will not refactor this code right now nor accept any PR that
changes the current design. I am busy in other parts of the code
base and do not have time to do the context switch required for
implementing this kind of change and/or review the PR and make sure I'm
happy with it.
@kha: I decided to implement this change before I start the
type_context modifications. The change did not affect the corelib and
test suite much. The only annoying problem is that `out` cannot be
used to name locals anymore.
