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4.19 Undefined

The constant #<undefined> is used as the initial value for letrec bindings and in other places where a placeholder value is needed before a specific value can be assigned. Use undefined (which is bound to #<undefined>) as a last resort.

The #<undefined> value is always eq? to itself.

 (require racket/undefined) package: base
The bindings documented in this section are provided by the racket/undefined library, not racket/base or racket.


undefined : any/c

The #<undefined> constant.

Added in version of package base.