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multiple-values-limit

multiple-values-limit Constant Variable

Constant Value:

An integer not smaller than 20, the exact magnitude of which is implementation-dependent.

Description:

The upper exclusive bound on the number of values that may be returned from a function, bound or assigned by multiple-value-bind or multiple-value-setq, or passed as a first argument to nth-value. (If these individual limits might di↵er, the minimum value is used.)

See Also:

lambda-parameters-limit, call-arguments-limit

Notes:

Implementors are encouraged to make this limit as large as possible.

Expanded Reference: multiple-values-limit​

Inspecting the Value​

multiple-values-limit is an upper exclusive bound on the number of values that can be returned from a function via values. The standard requires this to be at least 20.

;; Check the implementation's limit
multiple-values-limit
=> 1073741824

;; Guaranteed to be at least 20
(>= multiple-values-limit 20)
=> T

Returning Multiple Values​

In practice, values can return many values, but the limit determines the maximum your implementation supports.

;; Returning a modest number of values is always fine
(multiple-value-list (values 1 2 3 4 5))
=> (1 2 3 4 5)

;; The limit is typically very large
(format nil "Can return up to ~:D values" (1- multiple-values-limit))
=> "Can return up to 1,073,741,823 values"

Relationship to Other Limits​

multiple-values-limit may differ from call-arguments-limit and lambda-parameters-limit. It specifically governs values and multiple-value-bind.

(list :call-args call-arguments-limit
      :lambda-params lambda-parameters-limit
      :multiple-values multiple-values-limit)
=> (:CALL-ARGS 1073741824 :LAMBDA-PARAMS 1073741824 :MULTIPLE-VALUES 1073741824)