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<h5 class="subsubsection">3.6.2.3 Flonums</h5>
<p><a name="index-flonums-181"></a><a name="index-floating-point-numbers-182"></a><a name="index-constants_002c-floating-point-183"></a>
<a name="index-precision_002c-floating-point-184"></a>A <dfn>flonum</dfn> represents a floating point number. The translation is
indirect: a decimal floating point number from the text is converted by
<samp><span class="command">as</span></samp> to a generic binary floating point number of more than
sufficient precision. This generic floating point number is converted
to a particular computer's floating point format (or formats) by a
portion of <samp><span class="command">as</span></samp> specialized to that computer.
<p>A flonum is written by writing (in order)
<ul>
<li>The digit ‘<samp><span class="samp">0</span></samp>’.
(‘<samp><span class="samp">0</span></samp>’ is optional on the HPPA.)
<li>A letter, to tell <samp><span class="command">as</span></samp> the rest of the number is a flonum.
<kbd>e</kbd> is recommended. Case is not important.
<p>On the H8/300, Renesas / SuperH SH,
and AMD 29K architectures, the letter must be
one of the letters ‘<samp><span class="samp">DFPRSX</span></samp>’ (in upper or lower case).
<p>On the ARC, the letter must be one of the letters ‘<samp><span class="samp">DFRS</span></samp>’
(in upper or lower case).
<p>On the Intel 960 architecture, the letter must be
one of the letters ‘<samp><span class="samp">DFT</span></samp>’ (in upper or lower case).
<p>On the HPPA architecture, the letter must be ‘<samp><span class="samp">E</span></samp>’ (upper case only).
<li>An optional sign: either ‘<samp><span class="samp">+</span></samp>’ or ‘<samp><span class="samp">-</span></samp>’.
<li>An optional <dfn>integer part</dfn>: zero or more decimal digits.
<li>An optional <dfn>fractional part</dfn>: ‘<samp><span class="samp">.</span></samp>’ followed by zero
or more decimal digits.
<li>An optional exponent, consisting of:
<ul>
<li>An ‘<samp><span class="samp">E</span></samp>’ or ‘<samp><span class="samp">e</span></samp>’.
<!-- I can't find a config where "EXP_CHARS" is other than 'eE', but in -->
<!-- principle this can perfectly well be different on different targets. -->
<li>Optional sign: either ‘<samp><span class="samp">+</span></samp>’ or ‘<samp><span class="samp">-</span></samp>’.
<li>One or more decimal digits.
</ul>
</ul>
<p>At least one of the integer part or the fractional part must be
present. The floating point number has the usual base-10 value.
<p><samp><span class="command">as</span></samp> does all processing using integers. Flonums are computed
independently of any floating point hardware in the computer running
<samp><span class="command">as</span></samp>.
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