aref

(aref array &rest subscripts)

Returns the element of array at the given 0-based subscripts, one per dimension (one for a rank-1 vector, two for a rank-2 array, and so on). A string is a rank-1 character array, so (aref s i) reads like char (writing a string element goes through the schar/char setf place instead). Flat rank-independent access is available via row-major-aref. To modify an element, use aref as a setf place: (setf (aref array i j) value), which also works with incf/decf/push. #'aref is a first-class function value, so it can be passed to mapcar/funcall like any other function.