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Next: <a href="complex-_0028System-Class_0029.html" accesskey="n" rel="next">complex (System Class)</a>, Previous: <a href="Numbers-Dictionary.html" accesskey="p" rel="prev">Numbers Dictionary</a>, Up: <a href="Numbers-Dictionary.html" accesskey="u" rel="up">Numbers Dictionary</a> </p>
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<span id="number-_005bSystem-Class_005d"></span><h4 class="subsection">12.2.1 number [System Class]</h4>
<span id="Class-Precedence-List_003a_003a-35"></span><h4 class="subsubheading">Class Precedence List::</h4>
<p><b>number</b>,
<b>t</b>
</p>
<span id="Description_003a_003a-267"></span><h4 class="subsubheading">Description::</h4>
<p>The <i>type</i> <b>number</b> contains <i>objects</i> which represent
mathematical numbers.
</p>
<p>The <i>types</i> <b>real</b> and <b>complex</b> are <i>disjoint</i>
<i>subtypes</i> of <b>number</b>.
</p>
<p>The <i>function</i> <b>=</b> tests for numerical equality.
The <i>function</i> <b>eql</b>, when its arguments are both <i>numbers</i>,
tests that they have both the same <i>type</i> and numerical value.
Two <i>numbers</i> that are the <i>same</i> under <b>eql</b> or <b>=</b>
are not necessarily the <i>same</i> under <b>eq</b>.
</p>
<span id="Notes_003a_003a-136"></span><h4 class="subsubheading">Notes::</h4>
<p><span class="roman">Common Lisp</span> differs from mathematics on some naming issues. In mathematics,
the set of real numbers is traditionally described as a subset of the
complex numbers, but in <span class="roman">Common Lisp</span>, the <i>type</i> <b>real</b> and the <i>type</i> <b>complex</b> are
disjoint. The <span class="roman">Common Lisp</span> type which includes all mathematical complex
numbers is called <b>number</b>. The reasons for these differences
include historical precedent, compatibility with most other popular
computer languages, and various issues of time and space efficiency.
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