Aset1
Set the elements of a 1-dimensional array
Example Form:
(aset1 'delta1 a (+ i k) 27)
General Form:
(aset1 name alist index val)
where name is a symbol, alist is a 1-dimensional array named
name, index is a legal index into alist, and val is an
arbitrary object. See arrays for details. Roughly speaking this
function ``modifies'' alist so that the value associated with index
is val. More precisely, it returns a new array, alist', of the same
name and dimension as alist that, under aref1, is everywhere
equal to alist except at index where the result is val. That
is, (aref1 name alist' i) is (aref1 name alist i) for all legal
indices i except index, where (aref1 name alist' i) is
val.
In order to ``modify'' alist, aset1 conses a new pair
onto the front. If the length of the resulting alist exceeds the :maximum-length entry in the array header, aset1 compresses the
array as with compress1.
It is generally expected that the ``semantic value'' of name will be
alist (see arrays). This function operates in virtually constant
time whether this condition is true or not (unless the compress1
operation is required). But the value returned by this function cannot be
used efficiently by subsequent aset1 operations unless alist is the
semantic value of name when aset1 is executed. Thus, if the
condition is not true, aset1 prints a slow array warning to the
comment window. See slow-array-warning.
Note that aset1 is marked as having invariant-risk, which
can affect the execution of :program-mode functions. To get
around this problem (but only with great care!), see aset1-trusted.
Function: aset1
(defun
aset1 (name l n val)
(declare (xargs :guard (and (array1p name l)
(integerp n)
(>= n 0)
(< n (car (dimensions name l))))))
(let ((l (cons (cons n val) l)))
(cond ((> (length l) (maximum-length name l))
(compress1 name l))
(t l))))Subtopics
- Aset1-trusted
- Set the elements of a 1-dimensional array without invariant-risk
