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Robert Ramey 00e39147a4 Resolve problems with documentation 
a) missing concepts
b) missing examples
c) rationalized types
2015-06-10 22:46:58 -07:00

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<div class="titlepage"><div><div><h3 class="title">
<a name="safe_numerics.safe_compare"></a>safe_compare&lt;T, U&gt;</h3></div></div></div>
<div class="toc"><dl>
<dt><span class="section"><a href="safe_compare.html#idm354477307616">Synopsis</a></span></dt>
<dt><span class="section"><a href="safe_compare.html#idm354477305520">Description</a></span></dt>
<dt><span class="section"><a href="safe_compare.html#idm354477302976">Type requirements</a></span></dt>
<dt><span class="section"><a href="safe_compare.html#idm354477293424">Header</a></span></dt>
<dt><span class="section"><a href="safe_compare.html#idm354477291360">Example of use</a></span></dt>
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<div class="titlepage"><div><div><h4 class="title">
<a name="idm354477307616"></a>Synopsis</h4></div></div></div>
<p>safe_compare is several functions:.</p>
<pre class="programlisting">template&lt;class T, class U&gt;
bool safe_compare::less_than(const T &amp; lhs, const U &amp; rhs);
template&lt;class T, class U&gt;
bool safe_compare::less_than_equal(const T &amp; lhs, const U &amp; rhs);
template&lt;class T, class U&gt;
bool safe_compare::greater_than(const T &amp; lhs, const U &amp; rhs);
template&lt;class T, class U&gt;
bool safe_compare::greater_than_equal(const T &amp; lhs, const U &amp; rhs);
template&lt;class T, class U&gt;
bool safe_compare::equal(const T &amp; lhs, const U &amp; rhs);
template&lt;class T, class U&gt;
bool safe_compare::not_equal(const T &amp; lhs, const U &amp; rhs);</pre>
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<a name="idm354477305520"></a>Description</h4></div></div></div>
<p>With normal comparison operators, comparison of unsigned types to
signed types will be done by converting the unsigned type to a signed type
before comparing. Unfortunately this is not always possible. Most C++
compilers will emit an warning message when this is possible but won't
check that an error is made in the conversion. This function guarantees a
correct result regardless of the types of the arguments. It's used in the
implementation of the safe numerics library. It has been made publicly
accessible in because it might be useful in other contexts.</p>
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<a name="idm354477302976"></a>Type requirements</h4></div></div></div>
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<th align="left">Type</th>
<th align="left">Requirements</th>
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<td align="left"><code class="computeroutput">T</code></td>
<td align="left"><a class="link" href="numeric.html" title="Numeric&lt;T&gt;">Numeric</a></td>
</tr>
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<td align="left"><code class="computeroutput">U </code></td>
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<div class="titlepage"><div><div><h4 class="title">
<a name="idm354477293424"></a>Header</h4></div></div></div>
<p><a href="../../include/safe_compare.hpp" target="_top"><code class="filename">#include
&lt;boost/numeric/safe_compare.hpp&gt; </code></a></p>
</div>
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<div class="titlepage"><div><div><h4 class="title">
<a name="idm354477291360"></a>Example of use</h4></div></div></div>
<pre class="programlisting">#include &lt;boost/numeric/safe_compare.hpp&gt;
void f(){
unsigned char i = 129;
unsigned int j = 1;
assert(j &lt; i); // program traps because expression is false. But this is a surprise because 1 &lt; 129
assert( safe_compare::less_than(j,i)); // expression is true as we would expect
}
// safe_compare is used to implement comparison operators for safe types. So we can do this:
void g(){
safe&lt;unsigned char&gt; int i = 0x129;
safe&lt;int&gt; j = 1;
assert(j &lt; i); // program works as expected
}</pre>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2012 Robert Ramey<p><a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">Subject to Boost
Software License</a></p>
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