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The Lean Language Reference
1.
Introduction
2.
Elaboration and Compilation
3.
The Type System
4.
Interacting with Lean
5.
Source Files
6.
Recursive Definitions
7.
Terms
8.
Type Classes
9.
Functors, Monads and
do
-Notation
10.
IO
11.
Tactic Proofs
12.
The Simplifier
13.
Basic Propositions
14.
Basic Types
15.
Standard Library
16.
Notations and Macros
17.
Output from Lean
18.
Elan
19.
Build Tools and Distribution
Index
10.
IO
10.1.
Logical Model
10.2.
Control Structures
10.3.
Console Output
10.4.
Mutable References
10.5.
Files, File Handles, and Streams
10.6.
System and Platform Information
10.7.
Environment Variables
10.8.
Timing
10.9.
Processes
10.10.
Random Numbers
10.11.
Tasks and Threads
10.7.
Environment Variables
getEnv
Source Code
Report Issues
10.7. Environment Variables
🔗
🔗
opaque
IO.getEnv (
var
:
String
) :
BaseIO
(
Option
String
)