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Add a note about endl semantics 

llvm-svn: 1502
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Chris Lattner 2002-01-20 19:01:26 +00:00
parent f9dbd3926f
commit 850d4f6af1
1 changed files with 15 additions and 1 deletions
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llvm/docs/CodingStandards.html
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@ -37,6 +37,7 @@
<ol>
<li><a href="#hl_assert">Assert Liberally</a>
<li><a href="#hl_preincrement">Prefer Preincrement</a>
<li><a href="#hl_avoidendl">Avoid endl</a>
<li><a href="#hl_exploitcpp">Exploit C++ to its Fullest</a>
</ol>
<li><a href="#iterators">Writing Iterators</a>
@ -292,6 +293,19 @@ Hard fast rule: Preincrement (++X) may be no slower than postincrement (X++) and
The semantics of postincrement include making a copy of the value being incremented, returning it, and then preincrementing the "work value". For primitive types, this isn't a big deal... but for iterators, it can be a huge issue (for example, some iterators contains stack and set objects in them... copying an iterator could invoke the copy ctor's of these as well). In general, get in the habit of always using preincrement, and you won't have a problem.<p>
<!-- _______________________________________________________________________ -->
</ul><a name="hl_avoidendl"><h4><hr size=0>Avoid endl</h4><ul>
The <tt>endl</tt> modifier, when used with iostreams outputs a newline to the output stream specified. In addition to doing this, however, it also flushes the output stream. In other words, these are equivalent:<p>
<pre>
cout << endl;
cout << "\n" << flush;
</pre>
Most of the time, you probably have no reason to flush the output stream, so it's better to use a literal <tt>"\n"</tt>.<p>
<!-- _______________________________________________________________________ -->
</ul><a name="hl_exploitcpp"><h4><hr size=0>Exploit C++ to its Fullest</h4><ul>
@ -646,7 +660,7 @@ If you get some free time, and you haven't read them: do so, you might learn som
<address><a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
<!-- Created: Tue Jan 23 15:19:28 CST 2001 -->
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Last modified: Mon Oct 1 15:33:40 CDT 2001
Last modified: Sun Jan 20 13:01:02 CST 2002
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</font>
</body></html>