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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - APFloat::toString shouldn't print extra digits"
href="http://llvm.org/bugs/show_bug.cgi?id=17135">17135</a>
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<th>Summary</th>
<td>APFloat::toString shouldn't print extra digits
</td>
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<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Support Libraries
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>sharparrow1@yahoo.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=11151" name="attach_11151" title="WIP patch">attachment 11151</a> <a href="attachment.cgi?id=11151&action=edit" title="WIP patch">[details]</a></span>
WIP patch
As of r189624, calling APFloat::toString with the default arguments prints
enough digits of the value so that any float can be parsed back into the same
value which was printed (e.g. 17 digits for a double). However, this isn't
really ideal: most floats don't need that many digits to satisfy this
round-trip property.
Having a higher-quality implementation would be convenient for clang, in cases
where we want to print out a floating-point number accurately (for diagnostics
or AST printing) without overwhelming the user with extra digits. LLDB would
also find this useful in similar situations.
Attaching a WIP patch based on the Dragon4 algorithm from "How to Print
Floating-Point Numbers Accurately" by Steele and White, but it's a lot slower
than the current implementation, and I don't really have the expertise dealing
with floating-point numbers to know whether I'm even going in the right
direction.
(This is also tracked as <rdar://problem/14874559>.)</pre>
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