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<html><head>
<title>Arrays</title>
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<body>
<a href="../start.htm">Nyquist / XLISP 2.0</a> -
<a href="../manual/contents.htm">Contents</a> |
<a href="../tutorials/tutorials.htm">Tutorials</a> |
<a href="examples.htm">Examples</a> |
<a href="../reference/reference-index.htm">Reference</a>
<hr>
<h1>Arrays</h1>
<hr>
<p>Arrays are also <a href="sequences.htm">Sequences</a>.</p>
<ul>
<li><nobr><a href="#make-array-star">make-array*</a> - create multi-dimensional arrays</nobr></li>
<li><nobr><a href="#aref-star">aref*</a> - access multi-dimensional-arrays</nobr></li>
<li><nobr><a href="#vector-star">vector*</a> - make a one-dimensional array out of arbitrary Lisp expressions</nobr></li>
<li><nobr><a href="#vector-star">array*</a> - make a multi-dimensional array out of arbitrary Lisp expressions</nobr></li>
</ul>
<a name="make-array-star"></a>
<hr>
<h2>make-array*</h2>
<hr>
<p>XLISP already has the
<nobr><a href="../reference/make-array.htm">make-array</a></nobr>
function to create <nobr>one-dimensional</nobr> arrays:</p>
<p><div class="box">
<dl>
<dt><nobr>(<a href="../reference/make-array.htm">make-array</a> <i>size</i>)</nobr></dt>
<dd><i>size</i> - the size [integer] of the array to be created<br>
returns - the new array</dd>
</dl>
</div></p>
<p>Here is a function to create <nobr>multi-dimensional</nobr> arrays:</p>
<p><div class="box">
<dl>
<dt>(<b>make-array*</b> <i>size-1</i> [<i>size-2</i> ...])</dt>
<dd><i>sizeN</i> - the size [integer] of the <i>N</i>-th dimension in the array to be created<br>
returns - the new array</dd>
</dl>
</div></p>
<pre class="example">
(defun <font color="#0000CC">make-array*</font> (&rest dimensions-list)
(cond ((null dimensions-list)
(error <font color="#880000">"too few arguments"</font>))
((and (null (rest dimensions-list))
(eql 0 (first dimensions-list)))
(make-array 0))
(t (labels ((multi-vector (dimensions-list)
(let ((count (first dimensions-list)))
(if (not (and (integerp count) (plusp count)))
(error <font color="#880000">"not a positive integer"</font> count)
(let ((rest (rest dimensions-list))
(elements-list nil))
(dotimes (i count)
(push (when rest
(multi-vector rest))
elements-list))
(apply #'vector (reverse elements-list)))))))
(multi-vector dimensions-list)))))
</pre>
<p>Examples:</p>
<pre class="example">
(make-array* 2 3) => #(#(NIL NIL NIL) #(NIL NIL NIL)))
(make-array* 2 2 1) => #(#(#(NIL) #(NIL)) #(#(NIL) #(NIL)))
</pre>
<p>Like <nobr><a href="../reference/make-array.htm">make-array</a></nobr> it
is possible to create <nobr>one-dimensional</nobr> arrays with zero
elements:</p>
<pre class="example">
(make-array* 0) => #()
(make-array 0) => #()
</pre>
<p>But it is not allowed to create <nobr>multi-dimensional</nobr> arrays
with <nobr>zero-size</nobr> dimensions:</p>
<pre class="example">
(make-array* 1 0 1) => <font color="#AA0000">error: not a positive integer - 0</font>
</pre>
<p><b>Rationale:</b> Multi-dimensional arrays are implemented as nested
vectors and a <nobr>zero-element</nobr> vector cannot hold the vector for
the subsequent dimension. <nobr>We would</nobr> need some additional
administration overhead to keep the subsequent dimensions accessible, but
this would break the compatibility to the <nobr>build-in</nobr> XLISP
<a href="../reference/aref.htm">aref</a> function.</p>
<p>More practical examples see 'aref*' below.</p>
<p><nobr> <a href="#top">Back to top</a></nobr></p>
<a name="aref-star"></a>
<hr>
<h2>aref*</h2>
<hr>
<p>XLISP already has the <a href="../reference/aref.htm">aref</a> function
to access elements in one-dimensional arrays:</p>
<p><div class="box">
<dl>
<dt>(<a href="../reference/aref.htm">aref</a> <i>array dimension-1</i>)</dt>
<dd><i>array</i> - one-dimensional array<br>
<i>dimension-1</i> - element number in the first dimension<br>
returns - the value of the array element</dd>
</dl>
</div></p>
<p>Here is a macro for accessing elements in <nobr>multi-dimensional</nobr>
arrays:</p>
<p><div class="box">
<dl>
<dt>(<b>aref*</b> <i>array dimension-1</i> [<i>dimension-2</i> ...])</dt>
<dd><i>array</i> - any-dimensional array<br>
<i>dimensionN</i> - element number in the <i>N</i>-th dimension<br>
returns - the value of the array element</dd>
</dl>
</div></p>
<pre class="example">
(defmacro <font color="#0000CC">aref*</font> (array &rest index-list)
(labels ((multi-aref (array-name index-list)
(let ((index (first index-list)))
(if (not (integerp index))
(error <font color="#880000">"not an integer"</font> index)
(let ((rest (rest index-list))
(expansion-list (list 'aref)))
(push (if rest
(multi-aref array-name rest)
array-name)
expansion-list)
(push index expansion-list)
(reverse expansion-list))))))
(multi-aref `,array (reverse `,index-list))))
</pre>
<p>The symbols inside the <a href="../reference/labels.htm">labels</a> form
do not leak into the expansion, so 'aref*' also works with array names like
'array', '<nobr>array-name</nobr>' 'index', '<nobr>index-list</nobr>' or
'<nobr>expansion-list</nobr>'. Also the values of local or global variables
with these names are not changed.</p>
<pre class="example">
(macroexpand-1 '(aref* a 1 2 3)) => (aref (aref (aref a 1) 2) 3)
</pre>
<p>Examples:</p>
<pre class="example">
> (setq a (make-array* 2 3))
#(#(NIL NIL NIL) #(NIL NIL NIL)))
> (setf (aref* a 0 1) "hello")
"hello"
> a
#(#(NIL "hello" NIL) #(NIL NIL NIL))
> (aref* a 0 1)
"hello"
</pre>
<p>'aref*' with only one 'dimension' argument behaves
<nobr>like <a href="../reference/aref.htm">aref</a>:</nobr></p>
<pre class="example">
(aref* a 0) => #(NIL "hello" NIL)
(aref a 0) => #(NIL "hello" NIL)
(aref* (aref* a 0) 1) => "hello"
(aref (aref a 0) 1) => "hello"
(aref* a 0 1) => "hello"
(aref a 0 1) => <font color="#AA0000">error: too many arguments</font>
</pre>
<p>'aref*' like <a href="../reference/aref.htm">aref</a> also works
<nobr>with <a href="../reference/setf.htm">setf</a></nobr> to store
values in <nobr>multi-dimensional</nobr> arrays:</p>
<pre class="example">
(setf (aref* (aref* a 0) 1) "1") => "1" <font color="#008844">; a => #(#(NIL "1" NIL) #(NIL NIL NIL)))</font>
(setf (aref (aref a 0) 1) "2") => "2" <font color="#008844">; a => #(#(NIL "2" NIL) #(NIL NIL NIL)))</font>
(setf (aref* 0 1) "3") => "3" <font color="#008844">; a => #(#(NIL "3" NIL) #(NIL NIL NIL)))</font>
(setf (aref 0 1) "4") => <font color="#AA0000">error: too many arguments</font>
</pre>
<p><nobr> <a href="#top">Back to top</a></nobr></p>
<a name="vector-star"></a>
<hr>
<h2>vector*</h2>
<hr>
<pre class="example">
(defun <font color="#0000CC">vector*</font> (&rest items)
(if (null items)
(make-array 0)
(let* ((end (length items))
(result (make-array end)))
(if (> end 1)
(dotimes (index end) <font color="#008844">; more than one item</font>
(setf (aref result index)
(if (eq (nth index items) '*unbound*)
'*unbound*
(nth index items))))
(if (eq (first items) '*unbound*) <font color="#008844">; one item only</font>
(setf (aref result 0) '*unbound*)
(let ((item (first items)))
(case (type-of item)
(cons (let ((end (length item)))
(setq result (make-array end))
(dotimes (index end)
(setf (aref result index)
(if (eq (nth index item) '*unbound*)
'*unbound*
(nth index item))))))
(array (let ((end (length item)))
(setq result (make-array end))
(dotimes (index end)
(setf (aref result index)
(if (eq (aref item index) '*unbound*)
'*unbound*
(aref item index))))))
(string (let ((end (length item)))
(setq result (make-array end))
(dotimes (index end)
(setf (aref result index)
(char item index)))))
(t (setf (aref result 0) item))))))
result)))
</pre>
<pre class="example">
(defun <font color="#0000CC">list*</font> (&rest items)
(if (null items)
nil
(let* ((end (length items))
(result nil))
(labels ((push-element (element)
(if (member (type-of element) '(array cons string))
(setq result (append (reverse (list* element)) result))
(push element result))))
(dotimes (index end)
(if (eq (nth index items) '*unbound*)
(push '*unbound* result)
(let ((item (nth index items)))
(case (type-of item)
(nil (push item result))
(cons (let ((end (length item)))
(when (not (consp (last item))) (incf end))
(dotimes (index end)
(if (eq (nth index item) '*unbound*)
(push '*unbound* result)
(push-element (nth index item))))))
(array (let ((end (length item)))
(dotimes (index end)
(if (eq (aref item index) '*unbound*)
(push '*unbound* result)
(push-element (aref item index))))))
(string (let ((end (length item)))
(dotimes (index end)
(push (char item index) result))))
(t (push item result))))))
(reverse result)))))
</pre>
<pre class="example">
(defun <font color="#0000CC">tree*</font> (&rest items)
(if (null items)
nil
(let* ((end (length items))
(result nil))
(labels ((push-element (element)
(if (member (type-of element) '(array cons string))
(push (reverse (list* element)) result)
(push element result))))
(dotimes (index end)
(if (eq (nth index items) '*unbound*)
(push '*unbound* result)
(let ((item (nth index items)))
(case (type-of item)
(nil (push item result))
(cons (let ((end (length item)))
(when (not (consp (last item))) (incf end))
(dotimes (index end)
(if (eq (nth index item) '*unbound*)
(push '*unbound* result)
(push-element (nth index item))))))
(array (let ((end (length item)))
(dotimes (index end)
(if (eq (aref item index) '*unbound*)
(push '*unbound* result)
(push-element (aref item index))))))
(string (let ((end (length item)))
(dotimes (index end)
(push (char item index) result))))
(t (push item result))))))
(reverse result)))))
</pre>
<p><nobr> <a href="#top">Back to top</a></nobr></p>
<a name="array-star"></a>
<hr>
<h2>array*</h2>
<hr>
<pre class="example">
(defun <font color="#0000CC">array*</font> (&rest items)
(if (null items)
(make-array 0)
(let* ((end (length items))
(result (make-array end)))
(labels ((vector-element (element index)
(setf (aref result index)
(if (member (type-of element) '(cons string array))
(array* element)
element))))
(dotimes (index end)
(if (eq (nth index items) '*unbound*)
(setf (aref result index) '*unbound*)
(let ((item (nth index items)))
(case (type-of item)
(cons (let ((end (length item)))
(dotimes (index end)
(if (eq (nth index item) '*unbound*)
(strcat-element <font color="#880000">"*UNBOUND*"</font>)
(strcat-element (nth index item))))))
(array (let ((end (length item)))
(dotimes (index end)
(if (eq (aref item index) '*unbound*)
(strcat-element <font color="#880000">"*UNBOUND*"</font>)
(strcat-element (aref item index))))))
(t (strcat-element item))))))
result))))
</pre>
<p><nobr> <a href="#top">Back to top</a></nobr></p>
<hr>
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