boostorg/tuple
1
0
Fork 1
mirror of https://github.com/boostorg/tuple.git synced 2025-07-29 20:27:17 +02:00
Code Issues Packages Projects Releases Wiki Activity

Corrected/refined the requirement for a tuple element type

Browse Source 
[SVN r10975]
This commit is contained in:
Jaakko Järvi
2001-08-31 14:50:06 +00:00
parent 23a2b7ba58
commit 3bbc493fc1
1 changed files with 11 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
doc/tuple_users_guide.html
View File

@ -75,13 +75,22 @@ Both <code>tuple_io.hpp</code> and <code>tuple_comparison.hpp</code> include <co
The template parameters specify the types of the tuple elements.
The current version supports tuples with 0-10 elements.
If necessary, the upper limit can be increased up to, say, a few dozen elements.
The data element can be any C++ type, except for a type that cannot be copied, e.g.:
The data element can be any C++ type, except for a non-reference type
that is not copy constructible from a const qualified reference to that
same type. In practice this means, that the element type must be <i>CopyConstructible</i> [C++ Standard 20.1.3]. (To be precise, CopyConstrucible is an unnecessary strong requirement for a valid element type, as the <code>operator&amp;</code> is not used by the library.)
</p>
<p>
Examples of types that are not allowed as tuple elements:
<ul>
<li>classes that do not have a public copy constructor</li>
<li>classes, where the copy constructor takes its argument as a non-const reference (cf. <code>auto_ptr</code>)
<li>arrays</li>
</ul>
However, a reference to a non-copyable type is a valid element type.
Note that a reference to any of these non-copyable types is a valid element
type.
<p>
For example, the following definitions are valid tuple instantiations (<code>A</code>, <code>B</code> and <code>C</code> are some user defined classes):