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removed mention of Trivial Iterator

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[SVN r23231]
This commit is contained in:
Jeremy Siek
2004-06-28 13:26:05 +00:00
parent 9678d4a3f2
commit a29797eadc
1 changed files with 29 additions and 34 deletions
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concept_covering.htm
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@@ -35,46 +35,41 @@ component. If the program compiles then one can be sure that the
concepts cover the component. concepts cover the component.
The following code shows the archetype class for the <a The following code shows the archetype class for the <a
href="http://www.sgi.com/tech/stl/trivial.html">TrivialIterator</a> href="http://www.sgi.com/tech/stl/InputIterator.html">Input
concept. Some care must be taken to ensure that the archetype is an Iterator</a> concept. Some care must be taken to ensure that the
exact match to the concept. For example, the concept states that the archetype is an exact match to the concept. For example, the concept
return type of <tt>operator*()</tt> must be convertible to the value states that the return type of <tt>operator*()</tt> must be
type. It does not state the more stringent requirement that the return convertible to the value type. It does not state the more stringent
type be <tt>T&amp;</tt> or <tt>const T&amp;</tt>. That means it would be a requirement that the return type be <tt>T&amp;</tt> or <tt>const
mistake to use <tt>T&amp;</tt> or <tt>const T&amp;</tt> for the return type T&amp;</tt>. That means it would be a mistake to use <tt>T&amp;</tt>
of the archetype class. The correct approach is to create an or <tt>const T&amp;</tt> for the return type of the archetype
artificial return type that is convertible to <tt>T</tt>, as we have class. The correct approach is to create an artificial return type
done here with <tt>input_proxy</tt>. The validity of the archetype that is convertible to <tt>T</tt>, as we have done here with
class test is completely dependent on it being an exact match with the <tt>reference</tt>. The validity of the archetype class test is
concept, which must be verified by careful (manual) inspection. completely dependent on it being an exact match with the concept,
which must be verified by careful (manual) inspection.
<pre> <pre>
template &lt;class T&gt; template &lt;class T&gt;
struct input_proxy { class input_iterator_archetype
operator const T&() {
return static_object&lt;T&gt;::get(); // Get a reference without constructing
}
};
template &lt;class T&gt;
class trivial_iterator_archetype
{ {
typedef trivial_iterator_archetype self; private:
typedef input_iterator_archetype self;
public: public:
trivial_iterator_archetype() { } typedef std::input_iterator_tag iterator_category;
trivial_iterator_archetype(const self&) { }
self& operator=(const self&) { return *this; }
friend bool operator==(const self&, const self&) { return true; }
friend bool operator!=(const self&, const self&) { return true; }
input_proxy&lt;T&gt; operator*() { return input_proxy&lt;T&gt;(); }
};
namespace std {
template &lt;class T&gt;
struct iterator_traits&lt; trivial_iterator_archetype&lt;T&gt; &gt;
{
typedef T value_type; typedef T value_type;
struct reference {
operator const value_type&amp;() const { return static_object&lt;T&gt;::get(); }
};
typedef const T* pointer;
typedef std::ptrdiff_t difference_type;
self&amp; operator=(const self&amp;) { return *this; }
bool operator==(const self&amp;) const { return true; }
bool operator!=(const self&amp;) const { return true; }
reference operator*() const { return reference(); }
self&amp; operator++() { return *this; }
self operator++(int) { return *this; }
}; };
}
</pre> </pre>
Generic algorithms are often tested by being instantiated with a Generic algorithms are often tested by being instantiated with a