20 lines
1.6 KiB
Markdown
20 lines
1.6 KiB
Markdown
To Do List
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- ~~Add `cast : Pi (A B : Type) (H : A = B) (a : A) : B`, and implement "casting propagation" in the type checker.~~
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- ~~Modify the `let` construct to store the type of the value. The idea is to allow `let name : type := value in expr`. The type does not need to be provided by the user. However, the user may want to provide it as a hint for the Lean elaborator.~~
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- Refactor the elaborator code. The elaborator will be one of the main data-structures in Lean. The elaborator manager should be shared between different frontends.
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- Reconsider whether meta-variables should be in `expr` or not. Metavariables (aka holes) are fundamental in our [design](design.md).
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- ~~Improve Lean pretty printer for Pi's. For example, it produces `Var a : Pi (A : Type) (_ : A), A` instead of `Var a : Pi (A : Type), A -> A`.~~
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- Decide what will be the main technique for customizing Lean's behavior. The elaborator manager will have many building blocks that can be put together in many different ways. Possible solutions:
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- We design our own configuration language.
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- We use an off-the-shelf embedded language such as [Lua](http://www.lua.org).
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- We use Lean itself.
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- Module for reading OpenTheory proofs.
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- Higher-Order unification and matching.
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- Rewriter (and Rewriter Combinators).
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- MCSat framework.
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- Implement independent type checker using a different programming language (e.g., OCaml).
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- Add `match` construct in `expr`.
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- Add inductive datatype (families) in the environment. It will be a new kind of object.
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- Add recursive function definition objects (low priority). It is another new kind of object.
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