The Lean Language Reference
1.
Introduction
2.
Elaboration and Compilation
3.
The Lean Language
4.
Terms
5.
Monads and
do
-Notation
6.
IO
7.
Tactic Proofs
8.
The Simplifier
9.
Basic Types
10.
Standard Library
11.
Notations and Macros
12.
Elan
13.
Lake and Reservoir
Index
10.
Â
Standard Library
10.1.
Optional Values
10.1.
Â
Optional Values
10.1. Optional Values