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<title>N21zz C2X Proposal: Default rounding mode</title>
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<p><br>
<!-- Who are the authors... -->
<b>Submitter:</b>Fred J. Tydeman<br>
<!-- What is the date of submission. yyyy-mm-dd -->
<b>Submission Date:</b>2017-03-03<br>
<b>Document:</b> WG14 N21zz<br></p>
<p>Problem being solved</p>
<p>C11 makes several references to "default rounding mode". Yet,
there is no symbol for that mode. Also, the default rounding mode
need not be <b>FE_TONEAREST</b> (for example, IBM S/360 hex
floating-point is <b>FE_TOWARDZERO</b>).</p>
<p>Solution</p>
<p>In 7.6 paragraph 8, change</p>
<blockquote>
<p>Each of the macros</p>
<pre>
<b>
FE_DOWNWARD
FE_TONEAREST
FE_TOWARDZERO
FE_UPWARD
</b>
</pre>
</blockquote>to:
<blockquote>
<p>Each of the macros</p>
<pre>
<b>
FE_DOWNWARD
FE_TONEAREST
FE_TOWARDZERO
FE_UPWARD
FE_DEFAULT
</b>
</pre>
</blockquote>
<p>and change:</p>
<blockquote>
<p>The defined macros expand to integer constant expressions
whose values are distinct nonnegative values.211)</p>
</blockquote>
<p>to:</p>
<blockquote>
<p>The defined macros (except for <b>FE_DEFAULT</b>) expand to
integer constant expressions whose values are distinct
nonnegative values.211) <b>FE_DEFAULT</b> expands to a value of
one of the other <b>FE_*</b> macros and is the default rounding
mode.</p>
</blockquote>
<p>Add <b>FE_DEFAULT</b> to B.5 after <b>FE_TONEAREST</b>.</p>
<p>Add <b>FE_DEFAULT</b> to F.3 item about <b>fegetround</b>
before <b>FE_TONEAREST</b>.</p>
<p>Add <b>FE_DEFAULT</b> macro, <b>7.6</b> to the index.</p>
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