100 lines
4.5 KiB
HTML
100 lines
4.5 KiB
HTML
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<html lang="en">
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<head>
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<title>Flonums - Using as</title>
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<meta name="description" content="Using as">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Numbers.html#Numbers" title="Numbers">
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<link rel="prev" href="Bignums.html#Bignums" title="Bignums">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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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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</head>
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<body>
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<div class="node">
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<a name="Flonums"></a>
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<p>
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Previous: <a rel="previous" accesskey="p" href="Bignums.html#Bignums">Bignums</a>,
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Up: <a rel="up" accesskey="u" href="Numbers.html#Numbers">Numbers</a>
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<hr>
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</div>
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<h5 class="subsubsection">3.6.2.3 Flonums</h5>
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<p><a name="index-flonums-183"></a><a name="index-floating-point-numbers-184"></a><a name="index-constants_002c-floating-point-185"></a>
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<a name="index-precision_002c-floating-point-186"></a>A <dfn>flonum</dfn> 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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<samp><span class="command">as</span></samp> 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 <samp><span class="command">as</span></samp> specialized to that computer.
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<p>A flonum is written by writing (in order)
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<ul>
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<li>The digit ‘<samp><span class="samp">0</span></samp>’.
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(‘<samp><span class="samp">0</span></samp>’ is optional on the HPPA.)
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<li>A letter, to tell <samp><span class="command">as</span></samp> 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><span class="samp">DFPRSX</span></samp>’ (in upper or lower case).
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<p>On the ARC, the letter must be one of the letters ‘<samp><span class="samp">DFRS</span></samp>’
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(in upper or lower case).
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<p>On the HPPA architecture, the letter must be ‘<samp><span class="samp">E</span></samp>’ (upper case only).
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<li>An optional sign: either ‘<samp><span class="samp">+</span></samp>’ or ‘<samp><span class="samp">-</span></samp>’.
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<li>An optional <dfn>integer part</dfn>: zero or more decimal digits.
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<li>An optional <dfn>fractional part</dfn>: ‘<samp><span class="samp">.</span></samp>’ followed by zero
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or more decimal digits.
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<li>An optional exponent, consisting of:
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<ul>
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<li>An ‘<samp><span class="samp">E</span></samp>’ or ‘<samp><span class="samp">e</span></samp>’.
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<!-- I can't find a config where "EXP_CHARS" is other than 'eE', but in -->
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<!-- principle this can perfectly well be different on different targets. -->
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<li>Optional sign: either ‘<samp><span class="samp">+</span></samp>’ or ‘<samp><span class="samp">-</span></samp>’.
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<li>One or more decimal digits.
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</ul>
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</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><samp><span class="command">as</span></samp> 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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<samp><span class="command">as</span></samp>.
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</body></html>
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