Interactive Theorem Proving in Lean

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Lecture 4: Algebraic structures.

Florent Schaffhauser
Heidelberg University

Interactive Theorem Proving in Lean - Lecture 4
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--- ## Feedback on the workshop? And link to project file? Before we start working on the project files, I would like to ask for 5 minutes of your time, to give feedback on the workshop if you have not done it yet: ![Survey QR Code height:300](../../img/Feedback.svg) [Online survey](https://uni-heidelberg.evasys.de/evasys/online.php?p=WXQ8W) Thanks! :pray: :blush:

4. Formalise the definition of a group (by extending the `Monoid` structure). 5. Construct a group with underlying magma `⟨Int, (· + ·)⟩`. 6. Extend the definitions of monoids and groups to the commutative case and prove that `⟨Int, (· + ·)⟩` is a commutative group.