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127 lines
4.9 KiB
HTML
127 lines
4.9 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This file documents the GNU Assembler "as".
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Copyright (C) 1991-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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section entitled "GNU Free Documentation License".
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-->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Flonums (Using as)</title>
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<meta name="description" content="Flonums (Using as)">
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<meta name="keywords" content="Flonums (Using as)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="AS-Index.html#AS-Index" rel="index" title="AS Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Numbers.html#Numbers" rel="up" title="Numbers">
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<link href="Sections.html#Sections" rel="next" title="Sections">
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<link href="Bignums.html#Bignums" rel="prev" title="Bignums">
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<style type="text/css">
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a.summary-letter {text-decoration: none}
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pre.format {font-family: inherit}
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span.roman {font-family: initial; font-weight: normal}
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span.sansserif {font-family: sans-serif; font-weight: normal}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Flonums"></a>
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<div class="header">
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<p>
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Previous: <a href="Bignums.html#Bignums" accesskey="p" rel="prev">Bignums</a>, Up: <a href="Numbers.html#Numbers" accesskey="u" rel="up">Numbers</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Flonums-1"></a>
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<h4 class="subsubsection">3.6.2.3 Flonums</h4>
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<a name="index-flonums"></a>
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<a name="index-floating-point-numbers"></a>
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<a name="index-constants_002c-floating-point"></a>
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<a name="index-precision_002c-floating-point"></a>
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<p>A <em>flonum</em> represents a floating point number. The translation is
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indirect: a decimal floating point number from the text is converted by
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<code>as</code> to a generic binary floating point number of more than
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sufficient precision. This generic floating point number is converted
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to a particular computer’s floating point format (or formats) by a
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portion of <code>as</code> specialized to that computer.
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</p>
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<p>A flonum is written by writing (in order)
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</p><ul>
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<li> The digit ‘<samp>0</samp>’.
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(‘<samp>0</samp>’ is optional on the HPPA.)
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</li><li> A letter, to tell <code>as</code> the rest of the number is a flonum.
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<kbd>e</kbd> is recommended. Case is not important.
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<p>On the H8/300 and Renesas / SuperH SH architectures, the letter must be
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one of the letters ‘<samp>DFPRSX</samp>’ (in upper or lower case).
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</p>
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<p>On the ARC, the letter must be one of the letters ‘<samp>DFRS</samp>’
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(in upper or lower case).
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</p>
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<p>On the HPPA architecture, the letter must be ‘<samp>E</samp>’ (upper case only).
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</p>
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</li><li> An optional sign: either ‘<samp>+</samp>’ or ‘<samp>-</samp>’.
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</li><li> An optional <em>integer part</em>: zero or more decimal digits.
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</li><li> An optional <em>fractional part</em>: ‘<samp>.</samp>’ followed by zero
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or more decimal digits.
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</li><li> An optional exponent, consisting of:
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<ul>
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<li> An ‘<samp>E</samp>’ or ‘<samp>e</samp>’.
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</li><li> Optional sign: either ‘<samp>+</samp>’ or ‘<samp>-</samp>’.
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</li><li> One or more decimal digits.
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</li></ul>
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</li></ul>
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<p>At least one of the integer part or the fractional part must be
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present. The floating point number has the usual base-10 value.
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</p>
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<p><code>as</code> does all processing using integers. Flonums are computed
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independently of any floating point hardware in the computer running
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<code>as</code>.
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</p>
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</body>
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</html>
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