Loogle!

About

Loogle searches of Lean and Mathlib definitions and theorems.

You may also want to try the CLI version, the VS Code extension, the lean.nvim integration or the Zulip bot.

Usage

Loogle finds definitions and lemmas in various ways:

  1. By constant:
    🔍 Real.sin
    finds all lemmas whose statement somehow mentions the sine function.

  2. By lemma name substring:
    🔍 "differ"
    finds all lemmas that have "differ" somewhere in their lemma name.

  3. By subexpression:
    🔍 _ * (_ ^ _)
    finds all lemmas whose statements somewhere include a product where the second argument is raised to some power.

    The pattern can also be non-linear, as in
    🔍 Real.sqrt ?a * Real.sqrt ?a

    If the pattern has parameters, they are matched in any order. Both of these will find List.map:
    🔍 (?a -> ?b) -> List ?a -> List ?b
    🔍 List ?a -> (?a -> ?b) -> List ?b

  4. By main conclusion:
    🔍 |- tsum _ = _ * tsum _
    finds all lemmas where the conclusion (the subexpression to the right of all and ) has the given shape.

    As before, if the pattern has parameters, they are matched against the hypotheses of the lemma in any order; for example,
    🔍 |- _ < _ → tsum _ < tsum _
    will find tsum_lt_tsum even though the hypothesis f i < g i is not the last.

If you pass more than one such search filter, separated by commas Loogle will return lemmas which match all of them. The search
🔍 Real.sin, "two", tsum, _ * _, _ ^ _, |- _ < _ → _
woould find all lemmas which mention the constants Real.sin and tsum, have "two" as a substring of the lemma name, include a product and a power somewhere in the type, and have a hypothesis of the form _ < _ (if there were any such lemmas). Metavariables (?a) are assigned independently in each filter.

The #lucky button will directly send you to the documentation of the first hit.

Source code

You can find the source code for this service at https://github.com/nomeata/loogle. The https://loogle.lean-lang.org/ service is currently provided by Joachim Breitner <>.

This is Loogle revision c6903e4 serving mathlib revision 957ff69