APPLY Forms as Places (ANSI and GNU Common Lisp Document)

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#### 5.1.2.5 APPLY Forms as Places

The following situations involving setf of apply must be supported:

`*`

  `(setf (apply #'aref array {subscript}* more-subscripts) new-element)`

`*`

  `(setf (apply #'bit array {subscript}* more-subscripts) new-element)`

`*`

  `(setf (apply #'sbit array {subscript}* more-subscripts) new-element)`

In all three cases, the element of array designated by the concatenation of subscripts and more-subscripts (i.e., the same element which would be read by the call to apply if it were not part of a setf form) is changed to have the value given by new-element.

For these usages, the function name (aref, bit, or sbit) must refer to the global function definition, rather than a locally defined function.

No other standardized function is required to be supported, but an implementation may define such support. An implementation may also define support for implementation-defined operators.

If a user-defined function is used in this context, the following equivalence is true, except that care is taken to preserve proper left-to-right evaluation of argument subforms:

     (setf (apply #'name {arg}*) val)
     ≡ (apply #'(setf name) val {arg}*)