ANSI Common Lisp   5 Data and Control Flow   5.1 Generalized Reference   5.1.2 Kinds of Places

5.1.2.5 APPLY Forms as Places

• (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}*)