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<html><head>
<title>cl:equalp</title>
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<a href="../../start.htm">Nyquist / XLISP 2.0</a> -
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<hr>
<h1>cl:equalp</h1>
<hr>
<p><div class="box">
<dl>
<dt>(<b>equalp</b> <i>expr1 expr2</i>)</dt>
<dd><i>exprN</i> - arbitrary Lisp expressions<br>
returns - <a href="t.htm"> T </a> if the expressions
are structurally equal, <a href="nil.htm">NIL</a> otherwise</dd>
</dl>
</div></p>
<p>Two expressions are 'equalp':</p>
<ul>
<li><p>If the expressions
<nobr>are <a href="../../reference/equal.htm">equal</a></nobr>.</p></li>
<li><p>If two numbers of arbitrary type <nobr>are
<a href="../../reference/number-equal.htm"> = </a></nobr>.</p></li>
<li><p>If two characters are
<nobr><a href="../../reference/char-equal-i.htm">char-equal</a></nobr>.</p></li>
<li><p>If two strings are <nobr><a
href="../../reference/string-equal-i.htm">string-equal</a></nobr>.</p></li>
<li><p>If the two <a href="../../reference/car.htm">car</a>s in conses are
'equalp' and the two <a href="../../reference/cdr.htm">cdr</a>s in conses
are 'equalp'.</p></li>
<li><p>If two arrays have the same number of elements and dimensions, and
the corresponding elements in all dimensions are 'equalp'.</p></li>
</ul>
<p>Note that only 'equalp' can compare arrays.</p>
<pre class="example">
(defun <font color="#0000CC">cl:equalp</font> (expr-1 expr-2)
(or (equal expr-1 expr-2)
(and (numberp expr-1) (numberp expr-2) (= expr-1 expr-2))
(let ((type (type-of expr-1)))
(when (eq type (type-of expr-2))
(case type
(character (char-equal expr-1 expr-2))
(string (string-equal expr-1 expr-2))
(cons (do ((x (first expr-1)
(if (consp expr-1) (first expr-1) expr-1))
(y (first expr-2)
(if (consp expr-2) (first expr-2) expr-2)))
((or (null expr-1)
(null expr-2)
(not (equalp x y)))
(and (null expr-1)
(null expr-2)))
(setq expr-1 (and (consp expr-1) (rest expr-1))
expr-2 (and (consp expr-2) (rest expr-2)))))
(array (let ((end (length expr-1)))
(when (eql end (length expr-2))
(dotimes (index end t)
(and (not (equalp (aref expr-1 index)
(aref expr-2 index)))
(return nil)))))))))))
</pre>
<p><b>cons:</b> <a href="../../reference/do.htm">do</a> is used instead of
recursion because XLISP has only two kilobytes stack size. <nobr>The
(<a href="../../reference/consp.htm">consp</a> <i>expr</i>)</nobr> tests are
necessary because in a dotted list the last
<a href="../../reference/rest.htm">rest</a> element is not a cons.</p>
<p>Examples:</p>
<pre class="example">
(cl:equalp 1 1.0) => T
(cl:equalp #\a #\A) => T
(cl:equalp "Abc" "aBc") => T
(cl:equalp '(1 #\a "Abc") '(1.0 #\A "aBc")) => T
(cl:equalp #(1 #\a "Abc") #(1.0 #\A "aBc")) => T
</pre>
<p>Nested expressions only match if the nesting matches:</p>
<pre class="example">
(cl:equalp '(1 <font color="#AA0000">(</font>2 3<font color="#AA0000">)</font>) '(1.0 <font color="#AA0000">(</font>2.0 3.0<font color="#AA0000">)</font>) => T
(cl:equalp '(1 <font color="#AA0000">(</font>2 3<font color="#AA0000">)</font>) '(<font color="#AA0000">(</font>1.0 2.0<font color="#AA0000">)</font> 3.0) => NIL
(cl:equalp '(<font color="#AA0000">(</font>1 2<font color="#AA0000">)</font> 3) '(<font color="#AA0000">(</font>1.0 2.0<font color="#AA0000">)</font> 3.0) => T
(cl:equalp '(<font color="#AA0000">(</font>1 2<font color="#AA0000">)</font> 3) '(1.0 <font color="#AA0000">(</font>2.0 3.0<font color="#AA0000">)</font>) => NIL
</pre>
<p>A character does not match a string with the same character:</p>
<pre class="example">
(cl:equalp #\a "a") => NIL
</pre>
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