adjust-array

(adjust-array array new-dimensions &key initial-element fill-pointer)

Resizes array to new-dimensions (an integer for a vector, or a list of the same rank as array), preserving the elements at the subscripts valid in both shapes -- resizing a matrix keeps (i, j) at (i, j), not at the same flat position. New cells are set to :initial-element, defaulting to the array's element type's own zero -- the same fill make-array gives an unsupplied element: #\Space for a character array, 0 or 0.0 for a declared integer width or float type, nil for element type t. An array created :adjustable is adjusted in place and returned itself (eq to the argument), so every reference sees the new shape; otherwise a fresh array is returned -- use the return value either way. Without an explicit :fill-pointer the array's own fill pointer carries over (an error if it no longer fits); t sets it to the new size, an integer to that position. The element type is never changed: the fresh array a non-adjustable adjustment returns remembers what the original was asked to hold, so an adjusted character vector is still a string. A displaced argument is adjusted after it un-displaces: its current view contents become its own storage, so array-displacement answers nil and 0 on the result -- and, for a non-adjustable argument, on the original array too, since further use of the pre-adjustment array is unspecified either way. Passing :displaced-to to adjust-array itself is not supported and signals an error, and so is adjusting a packed integer vector. The new dimensions are checked as make-array checks its own, and one it refuses is reported under MAKE-ARRAY.