lean-mathlib-search

To find Mathlib lemmas for a Lean 4 proof goal, use a multi-tool workflow combining exact?, apply?, #leansearch, #loogle, and #check. This validates candidate lemmas quickly by leveraging the Batteries catalog and Mathlib search guide.

The best way to search for lemmas in Lean 4 Mathlib and Batteries is using REPL-assisted lookup. This workflow applies exact? and apply? for direct resolution, then uses #leansearch and #loogle to discover and verify candidate lemmas.

Yes, you can use exact? and apply? to automatically close Lean 4 goals with Mathlib. They serve as the primary tools for finding exact matching lemmas or applying hypotheses, supplemented by #leansearch and #loogle for broader discovery.

Yes, you need access to Mathlib, Batteries, and the REPL references described in the Mathlib search guide to reliably verify candidate lemmas. The REPL environment executes the multi-tool workflow to validate search results for your proof tasks.

A Lean 4 lemma search may fail if the query is too specific or the lemma is named differently. Broadening the search using #leansearch and #loogle, or checking lemma types with #check, helps locate relevant Mathlib/Batteries candidates that exact? might miss.