array - an array.
new-dimensions - a valid array dimension
or a list of valid array dimensions.
element-type - a type specifier.
initial-element - an object.
Initial-element must not be supplied if either
initial-contents or displaced-to is supplied.
initial-contents - an object.
If array has rank greater than zero, then initial-contents
is composed of nested sequences, the depth of which must equal
the rank of array. Otherwise, array is zero-dimensional and
initial-contents supplies the single element.
initial-contents must not be supplied if either
initial-element or displaced-to is given.
fill-pointer - a valid fill pointer for the
array to be created, or t, or nil.
The default is nil.
displaced-to - an array or nil.
initial-elements and initial-contents must not be supplied
if displaced-to is supplied.
displaced-index-offset - an object of type (fixnum 0 n)
where n is (array-total-size displaced-to).
displaced-index-offset may be supplied only if displaced-to is supplied.
adjusted-array - an array.
adjust-array changes the dimensions or elements of array.
The result is an array of the same type and rank as array,
that is either the modified array,
or a newly created array to which
array can be displaced, and that has
the given new-dimensions.
New-dimensions specify the size of each dimension of array.
Element-type specifies the type of the elements
of the resulting array. If element-type is supplied,
the consequences are unspecified if
the upgraded array element type of element-type
is not the same as the actual array element type of array.
If initial-contents is supplied, it is treated as for
make-array. In this case none of the original contents of
array appears in the resulting array.
If fill-pointer is an integer,
it becomes the fill pointer for the resulting array.
If fill-pointer is the symbol t,
it indicates that the size of the resulting array
should be used as the fill pointer.
If fill-pointer is nil,
it indicates that the fill pointer should be left as it is.
If displaced-to
non-nil, a displaced array
is created. The resulting array shares its contents with the array given by
displaced-to.
The resulting array cannot contain more elements than the array
it is displaced to.
If displaced-to is not supplied or nil,
the resulting array is not a displaced array.
If array A is created displaced to array B and subsequently
array B is given to adjust-array, array A will still be
displaced to array B.
Although array might be a displaced array,
the resulting array is not a displaced array unless
displaced-to is supplied and not nil.
The interaction between adjust-array and
displaced arrays
is as follows given three arrays, A, B, and C:
- A is not displaced before or after the call
(adjust-array A ...)
The dimensions of A are altered, and the
contents rearranged as appropriate.
Additional elements of A are taken from
initial-element.
The use of initial-contents causes all old contents to be
discarded.
- A is not displaced before, but is displaced to
C after the call
(adjust-array A ... :displaced-to C)
None of the original contents of A appears in
A afterwards; A now contains
the contents of C, without any rearrangement of C.
- A is displaced to B
before the call, and is displaced to C after
the call
(adjust-array A ... :displaced-to B)
(adjust-array A ... :displaced-to C)
B and C might be the same. The contents of B do not appear in
A afterward unless such contents also happen to be in C If
displaced-index-offset
is not supplied in the adjust-array call, it defaults
to zero; the old offset into B is not retained.
- A is displaced to B before the call, but not displaced
afterward.
(adjust-array A ... :displaced-to B)
(adjust-array A ... :displaced-to nil)
A gets a
new "data region," and contents of B are copied into it as appropriate to
maintain the existing old contents; additional elements of A
are taken from
initial-element if supplied. However,
the use of initial-contents causes all old contents
to be discarded.
If displaced-index-offset is supplied,
it specifies the offset
of the resulting array from the beginning of
the array that it is displaced to.
If displaced-index-offset is not supplied, the offset is 0.
The size of the resulting array plus the
offset value cannot exceed the size of
the array that it is displaced to.
If only new-dimensions
and an initial-element argument are supplied,
those elements of array that
are still in bounds appear in the resulting array. The elements of
the resulting array that are not in the bounds of
array are initialized
to initial-element; if initial-element is not provided,
the consequences of later reading any such new element of new-array
before it has been initialized
are undefined.
If initial-contents or displaced-to is supplied,
then none of the original contents of array appears in the new array.
The consequences are unspecified if array is adjusted
to a size smaller than its fill pointer without supplying
the fill-pointer argument so that its fill-pointer
is properly adjusted in the process.
If A is displaced to B, the consequences are unspecified
if B is adjusted in such a way that it no longer has enough elements
to satisfy A.
If adjust-array is applied to an array that is actually adjustable,
the array returned is identical to array.
If the array returned by adjust-array
is distinct from array, then the argument array is unchanged.
Note that if an array A is displaced to another array B,
and B is displaced to another array C, and B is altered by
adjust-array, A must now refer to the adjust contents of B.
This means that an implementation cannot collapse the chain to make A
refer to C directly and forget that the chain of reference passes through
B. However, caching techniques are permitted as long as they preserve the
semantics specified here.
(adjustable-array-p
(setq ada (adjust-array
(make-array '(2 3)
:adjustable t
:initial-contents '((a b c) (1 2 3)))
'(4 6)))) 
T
(array-dimensions ada) (4 6)
(aref ada 1 1) 2
(setq beta (make-array '(2 3) :adjustable t))
#2A((NIL NIL NIL) (NIL NIL NIL))
(adjust-array beta '(4 6) :displaced-to ada)
#2A((A B C NIL NIL NIL)
(1 2 3 NIL NIL NIL)
(NIL NIL NIL NIL NIL NIL)
(NIL NIL NIL NIL NIL NIL))
(array-dimensions beta) (4 6)
(aref beta 1 1) 2
Suppose that the 4-by-4 array in m looks like this:
#2A(( alpha beta gamma delta )
( epsilon zeta eta theta )
( iota kappa lambda mu )
( nu xi omicron pi ))
Then the result of
(adjust-array m '(3 5) :initial-element 'baz)
is a 3-by-5 array with contents
#2A(( alpha beta gamma delta baz )
( epsilon zeta eta theta baz )
( iota kappa lambda mu baz ))
15 Arrays