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<title>Issue 205:  numeric_limits unclear on how to determine floating point types</title>
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<p><em>This page is a snapshot from the LWG issues list, see the <a href="lwg-active.html">Library Active Issues List</a> for more information and the meaning of <a href="lwg-active.html#NAD">NAD</a> status.</em></p>
<h3 id="205"><a href="lwg-closed.html#205">205</a>.  numeric_limits unclear on how to determine floating point types</h3>
<p><b>Section:</b> 17.3.5.2 <a href="https://wg21.link/numeric.limits.members">[numeric.limits.members]</a> <b>Status:</b> <a href="lwg-active.html#NAD">NAD</a>
 <b>Submitter:</b> Steve Cleary <b>Opened:</b> 2000-01-28 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#numeric.limits.members">issues</a> in [numeric.limits.members].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#NAD">NAD</a> status.</p>
<p><b>Discussion:</b></p>
<p>In several places in 17.3.5.2 <a href="https://wg21.link/numeric.limits.members">[numeric.limits.members]</a>, a member is
described as &quot;Meaningful for all floating point types.&quot;
However, no clear method of determining a floating point type is
provided.</p>

<p>In 17.3.5.3 <a href="https://wg21.link/numeric.special">[numeric.special]</a>, paragraph 1 states &quot;. . . (for
example, epsilon() is only meaningful if is_integer is
false). . .&quot; which suggests that a type is a floating point type
if is_specialized is true and is_integer is false; however, this is
unclear.</p>

<p>When clarifying this, please keep in mind this need of users: what
exactly is the definition of floating point? Would a fixed point or
rational representation be considered one? I guess my statement here
is that there could also be types that are neither integer or
(strictly) floating point.</p>


<p><b>Rationale:</b></p>
<p>It is up to the implementor of a user define type to decide if it is a
floating point type.</p>




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