4.18 Void and Undefined

The constant #<void> is returned by most forms and procedures that have a side-effect and no useful result. The constant #<undefined> is used as the initial value for letrec bindings.

The #<void> value is always eq? to itself, and the #<undefined> value is also eq? to itself.

procedure
(void? v) → void?
v : any/c

Returns #t if v is the constant #<void>, #f otherwise.

procedure
(void v ...) → void?
v : any/c

Returns the constant #<void>. Each v argument is ignored.

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1	Language Model
2	Notation for Documentation
3	Syntactic Forms
4	Datatypes
5	Structures
6	Classes and Objects
7	Units
8	Contracts
9	Pattern Matching
10	Control Flow
11	Concurrency and Parallelism
12	Macros
13	Input and Output
14	Reflection and Security
15	Operating System
16	Memory Management
17	Unsafe Operations
18	Running Racket
	Bibliography
	Index

4.1	Booleans and Equality
4.2	Numbers
4.3	Strings
4.4	Byte Strings
4.5	Characters
4.6	Symbols
4.7	Regular Expressions
4.8	Keywords
4.9	Pairs and Lists
4.10	Mutable Pairs and Lists
4.11	Vectors
4.12	Boxes
4.13	Hash Tables
4.14	Sequences and Streams
4.15	Dictionaries
4.16	Sets
4.17	Procedures
4.18	Void and Undefined