Try doing some basic maths questions in the Lean Theorem Prover. Functions, real numbers, equivalence relations and groups. Click on README.md and then on "Open in CoCalc with one click".
License: APACHE
/-
Copyright (c) 2018 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Author: Mario Carneiro
Supplementary theorems about the `char` type.
-/
instance : decidable_linear_order char :=
{ le_refl := λ a, @le_refl ℕ _ _,
le_trans := λ a b c, @le_trans ℕ _ _ _ _,
le_antisymm := λ a b h₁ h₂,
char.eq_of_veq $ le_antisymm h₁ h₂,
le_total := λ a b, @le_total ℕ _ _ _,
lt_iff_le_not_le := λ a b, @lt_iff_le_not_le ℕ _ _ _,
decidable_le := char.decidable_le,
decidable_eq := char.decidable_eq,
decidable_lt := char.decidable_lt,
..char.has_le, ..char.has_lt }