Lean 3's obsolete mathematical components library: please use mathlib4
Lean 3's mathlib is a library for the Lean theorem prover that is no longer actively maintained. It is recommended to use mathlib4 for Lean 4 instead.
Mathlib 3 is a library for the Lean theorem prover that is no longer actively maintained. It is recommended to switch to mathlib4 for Lean 4, as it is the actively maintained version. Mathlib provides an extensive library of formalized mathematics and is a community-driven project. To install mathlib4, follow the provided installation guide.