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102 lines
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<a name="Flonums"></a>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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<h5 class="subsubsection">3.6.2.3 Flonums</h5>
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<p><a name="index-flonums-181"></a><a name="index-floating-point-numbers-182"></a><a name="index-constants_002c-floating-point-183"></a>
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<a name="index-precision_002c-floating-point-184"></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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<span class="command">as</span> 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 <span class="command">as</span> 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 <span class="samp">0</span>.
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(<span class="samp">0</span> is optional on the HPPA.)
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<li>A letter, to tell <span class="command">as</span> 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, Renesas / SuperH SH,
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and AMD 29K architectures, the letter must be
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one of the letters <span class="samp">DFPRSX</span> (in upper or lower case).
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<p>On the ARC, the letter must be one of the letters <span class="samp">DFRS</span>
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(in upper or lower case).
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<p>On the Intel 960 architecture, the letter must be
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one of the letters <span class="samp">DFT</span> (in upper or lower case).
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<p>On the HPPA architecture, the letter must be <span class="samp">E</span> (upper case only).
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<li>An optional sign: either <span class="samp">+</span> or <span class="samp">-</span>.
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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>: <span class="samp">.</span> 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 <span class="samp">E</span> or <span class="samp">e</span>.
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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 <span class="samp">+</span> or <span class="samp">-</span>.
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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><span class="command">as</span> 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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<span class="command">as</span>.
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