Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
5605735137
We add helper classes with `outParam`.
@Kha This is similar to the `MonadExceptOf` modification.
Motivation: the new `StateRefT` (state monad implemented using
`IO.Ref`) makes is it quite cheap to have multiple states on the
stack. But, we need a mechanism for accessing the different states in
a convenient way.
Note that, I did not add a `MonadStateOf` class, but helper classes
such as `HasGet` which uses `outParam`. I will do the same for `MonadExcept`.
Summary:
- `get` gets the state on the top of the Monad stack
- `getThe σ` gets the state with type `σ`
- `modify f` modifies the state on the top of the Monad stack.
We use `modify fun s => { s with ... }` quite often, and we cannot
infer type of `s` here.
- `modifyThe σ f` allows us to select which state on the stack we are modifying.
- I didn't add `setThe`, since we usually can infer the state type at
`set s`. In the whole codebase, we have only one instance where this
is not true.
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We are currently developing Lean 4. Lean 3 is still the latest official release. This repository contains work in progress.
Important. Unless you are one of our collaborators
- We strongly suggest you use Lean 3.
- Pull requests are not welcome.
- New issues are not welcome, and will be closed without any feedback.