docsrc/xlisp/xlisp-doc/reference/round.htm


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<html><head><title>XLISP round</title>

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</head>

<body>

<a href="../start.htm">Nyquist / XLISP 2.0</a>&nbsp; -&nbsp;
<a href="../manual/contents.htm">Contents</a> |
<a href="../tutorials/tutorials.htm">Tutorials</a> |
<a href="../examples/examples.htm">Examples</a> |
<a href="reference-index.htm">Reference</a>

<hr>

<h1>round</h1>

<hr>

<p><table cellpadding="0" cellspacing="0" style="margin-left:10px"><tbody>
<tr valign="top">
  <td><nobr>Type:</nobr></td>
  <td><nobr>&nbsp;&nbsp;-&nbsp;&nbsp;</nobr></td>
  <td width="100%"><nobr>Lisp function (closure)</nobr></td>
</tr>
<tr valign="top">
  <td><nobr>Source:</nobr></td>
  <td><nobr>&nbsp;&nbsp;-&nbsp;&nbsp;</nobr></td>
  <td width="100%"><nobr>fileio.lsp</nobr></td>
</tr>
</tbody></table></p>

<h2>Syntax</h2>

<p><div class="box">

<dl>
<dt><nobr>(<b>round</b> <i>number</i>)</nobr></dt>
<dd><i>number</i> - an integer or floating point numbers<br>
returns - the number, rounded to the next integer value</dd>
</dl>

</div></p>

<p>In Nyquist, 'round' is implemented as a Lisp function:</p>

<pre class="example">
(defun <font color="#0000CC">round</font> (x) 
  (cond ((> x 0) (truncate (+ x 0.5)))
        ((= (- x 0.5) (truncate (- x 0.5))) (truncate x))
        (t (truncate (- x 0.5)))))
</pre>

<h2>Description</h2>

<p>The 'round' function rounds a number to the next integer value. This is
tricky because <a href="truncate.htm">truncate</a> rounds toward zero as
<nobr>does C</nobr> in other words, rounding is down for positive numbers
and up for negative numbers. <nobr>You can</nobr> convert rounding up to
rounding down by subtracting one, but this fails on the integers, so we need
a special test if <nobr>(- x 0.5)</nobr> is an integer.</p>

<h2>Examples</h2>

<pre class="example">
(round .5)   =&gt; 1
(round -.5)  =&gt; 0
</pre>

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