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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 Types
14.
Standard Library
15.
Notations and Macros
16.
Output from Lean
17.
Elan
18.
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.
Environment Variables
10.7.
Timing
10.8.
Processes
10.9.
Random Numbers
10.10.
Tasks and Threads
10.6.
Environment Variables
getEnv
Source Code
Report Issues
10.6. Environment Variables
🔗
🔗
opaque
IO.getEnv (var :
String
) :
BaseIO
(
Option
String
)