The function foreign-array-element-type
takes a FLI array, a pointer to a FLI array or the name of a FLI array type as its argument and returns the type of the elements of that array.
In the following example a 3 by 4 array with integer elements is defined, and the foreign-array-element-type
function is used to confirm that the elements of the array are indeed integers.
(setq array1 (fli:allocate-foreign-object
:type '(:c-array :int 3 4)))
(fli:foreign-array-element-type array1)
LispWorks Foreign Language Interface User Guide and Reference Manual - 29 Sep 2017