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The Lean Language Reference
1.
Introduction
2.
Elaboration and Compilation
3.
The Type System
4.
Source Files
5.
Terms
6.
Type Classes
7.
Functors, Monads and
do
-Notation
8.
IO
9.
Tactic Proofs
10.
The Simplifier
11.
Basic Types
12.
Standard Library
13.
Notations and Macros
14.
Output from Lean
15.
Elan
16.
Lake and Reservoir
Index
8.
IO
8.1.
Logical Model
8.2.
Control Structures
8.3.
Console Output
8.4.
Mutable References
8.5.
Files, File Handles, and Streams
8.6.
Environment Variables
8.7.
Timing
8.8.
Processes
8.9.
Random Numbers
8.10.
Tasks and Threads
8.6.
Environment Variables
Source Code
Report Issues
8.6. Environment Variables
🔗
opaque
IO.getEnv (var :
String
) :
BaseIO
(
Option
String
)