<html>
<head>
<base href="http://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Can't std::sort a collection of std::pair if one pair element is const"
href="http://llvm.org/bugs/show_bug.cgi?id=19085">19085</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Can't std::sort a collection of std::pair if one pair element is const
</td>
</tr>
<tr>
<th>Product</th>
<td>libc++
</td>
</tr>
<tr>
<th>Version</th>
<td>3.3
</td>
</tr>
<tr>
<th>Hardware</th>
<td>Macintosh
</td>
</tr>
<tr>
<th>OS</th>
<td>MacOS X
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>hhinnant@apple.com
</td>
</tr>
<tr>
<th>Reporter</th>
<td>james@weatherley.net
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu, mclow.lists@gmail.com
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>#include <iostream>
#include <vector>
int main(int argc, const char * argv[])
{
// Replace the std::vector declaration with the commented out one and it
builds.
//
//std::vector<std::pair<int, int>> vec = {
std::vector<std::pair<const int, int>> vec = {
std::make_pair(9, 8),
std::make_pair(7, 6),
std::make_pair(5, 4),
std::make_pair(3, 2)
};
std::sort(vec.begin(), vec.end(), [](const std::pair<const int, int>& p1,
const std::pair<const int, int>&p2) {
return true;
});
for(auto pair:vec)
{
std::cout << pair.first << " : " << pair.second << "\n";
}
}
Build the above and you get errors:
/Applications/Xcode5.0/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/utility:292:15:
Read-only variable is not assignable
/Applications/Xcode5.0/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/utility:255:15:
Read-only variable is not assignable
I'm sorting - why does it want to assign to the const int pair element? Change
the pair declaration to a pair of non-const ints and it builds just fine.</pre>
</div>
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