Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
06ad52575a
After this commit, we have to use an explicit `discard` in code such as ``` def g (x : Nat) : IO Nat := ... def f (x : Nat) : IO Unit := do discard <| g x -- type error without the `discard` IO.println x ``` Motivation: prevent users from making mistakes such as ``` def f (xs : Array Nat) : IO Unit := do xs.set! 0 1 IO.println xs ``` when they meant to write ``` def f (xs : Array Nat) : IO Unit := do let xs := xs.set! 0 1 IO.println xs ``` |
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We are currently developing Lean 4. The Lean 4 manual (work in progress) will give you an overview of the language.
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.