<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Issue 481: unique's effects on the range [result, last)</title>
<meta property="og:title" content="Issue 481: unique's effects on the range [result, last)">
<meta property="og:description" content="C++ library issue. Status: NAD">
<meta property="og:url" content="https://cplusplus.github.io/LWG/issue481.html">
<meta property="og:type" content="website">
<meta property="og:image" content="http://cplusplus.github.io/LWG/images/cpp_logo.png">
<meta property="og:image:alt" content="C++ logo">
<style>
  p {text-align:justify}
  li {text-align:justify}
  pre code.backtick::before { content: "`" }
  pre code.backtick::after { content: "`" }
  blockquote.note
  {
    background-color:#E0E0E0;
    padding-left: 15px;
    padding-right: 15px;
    padding-top: 1px;
    padding-bottom: 1px;
  }
  ins {background-color:#A0FFA0}
  del {background-color:#FFA0A0}
  table.issues-index { border: 1px solid; border-collapse: collapse; }
  table.issues-index th { text-align: center; padding: 4px; border: 1px solid; }
  table.issues-index td { padding: 4px; border: 1px solid; }
  table.issues-index td:nth-child(1) { text-align: right; }
  table.issues-index td:nth-child(2) { text-align: left; }
  table.issues-index td:nth-child(3) { text-align: left; }
  table.issues-index td:nth-child(4) { text-align: left; }
  table.issues-index td:nth-child(5) { text-align: center; }
  table.issues-index td:nth-child(6) { text-align: center; }
  table.issues-index td:nth-child(7) { text-align: left; }
  table.issues-index td:nth-child(5) span.no-pr { color: red; }
  @media (prefers-color-scheme: dark) {
     html {
        color: #ddd;
        background-color: black;
     }
     ins {
        background-color: #225522
     }
     del {
        background-color: #662222
     }
     a {
        color: #6af
     }
     a:visited {
        color: #6af
     }
     blockquote.note
     {
        background-color: rgba(255, 255, 255, .10)
     }
  }
</style>
</head>
<body>
<hr>
<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="481"><a href="lwg-closed.html#481">481</a>. unique's effects on the range [result, last)</h3>
<p><b>Section:</b> 26.7.9 <a href="https://wg21.link/alg.unique">[alg.unique]</a> <b>Status:</b> <a href="lwg-active.html#NAD">NAD</a>
 <b>Submitter:</b> Andrew Koenig <b>Opened:</b> 2004-08-30 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#alg.unique">active issues</a> in [alg.unique].</p>
<p><b>View all other</b> <a href="lwg-index.html#alg.unique">issues</a> in [alg.unique].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#NAD">NAD</a> status.</p>
<p><b>Discussion:</b></p>
<p>
The standard says that unique(first, last) "eliminates all but the
first element from every consecutive group of equal elements" in
[first, last) and returns "the end of the resulting range".  So a
postcondition is that [first, result) is the same as the old [first,
last) except that duplicates have been eliminated.
</p>

<p>What postconditions are there on the range [result, last)?  One
  might argue that the standard says nothing about those values, so
  they can be anything.  One might also argue that the standard
  doesn't permit those values to be changed, so they must not be.
  Should the standard say something explicit one way or the other?</p>



<p id="res-481"><b>Proposed resolution:</b></p>
<p>
</p>


<p><b>Rationale:</b></p>
<p>We don't want to make many guarantees about what's in [result,
end). Maybe we aren't being quite explicit enough about not being
explicit, but it's hard to think that's a major problem.</p>





</body>
</html>
