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test/doc/components/test_tools/reference/BOOST_CHECK_CLOSE.html
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<H3>BOOST_CHECK_CLOSE( left, right, tolerance_src )</H3>
<P class="first_line_indented">This tool is used to check <I>left</I> and <I>right</I> values on closeness
using strong relationship defined by the predicate <A href="../floating_point_comparison.html" target="_top">close_at_tolerance
</A>( tolerance_src ). To check for the weak relationship use <A href="BOOST_CHECK_PREDICATE.html">BOOST_CHECK_PREDICATE</A>
tool. Note that to use this tool you need to include additional header<A href="../../../../../../boost/test/floating_point_comparison.hpp">
floating_point_comparison.hpp</A>, since tools implementation depends on this file that does not get
included automatically to minimize code dependency. </P>
<P class="first_line_indented">If comparison is successful, the tool produces a conformation message
(note: to manage what messages appear in the test output stream set the proper log level) in other
case it produces an error message in a form &quot;error in &lt;test case name&gt;: test &lt;<I>left</I>
argument name&gt; (==) &lt;<I>right</I> argument name&gt; failed [ &lt;<I>left</I> argument value&gt;
!= &lt;<I>right</I> argument value&gt; (&lt;real predicate value&gt;)]&quot;.</P>
<P class="first_line_indented"></P>
<P class="first_line_indented">The tool's first parameter is the <I>left</I> compared value. The tool's
second parameter is the <I>right</I> compared value. Last third parameter defines the tolerance for
the comparison. It could be floating point or integer value. For more details how to treat this value
see <A href="../floating_point_comparison.html" target="_top">close_at_tolerance </A>description.
Note that it required for <I>left</I> and <I>right</I> parameters to be of the same floating point
type. You need to explicitly resolve any type mismatch to select which type to use for comparison.</P>
<H4>Example: test.cpp</H4>
<PRE class="code"><SPAN class="cpp-type">int</SPAN> test_main( <SPAN class="cpp-type">int</SPAN>, <SPAN class="cpp-type">char</SPAN>* [] ) {
<SPAN class="cpp-type">double</SPAN> v1 = <SPAN class="literal">1.23456e-10</SPAN>;
<SPAN class="cpp-type">double</SPAN> v2 = <SPAN class="literal">1.23457e-10</SPAN>;
BOOST_CHECK_CLOSE( v1, v2, <SPAN class="literal">1e-6</SPAN> ); <SPAN class="comment">// should fail at tolerance supplied</SPAN>
<SPAN class="reserv-word">return</SPAN> <SPAN class="literal">0</SPAN>;
}</PRE>
<H4>Output:</H4>
<P class="test-output">test.cpp(4) : error in test_main: test v1 (==) v2 failed [1.23456e-10 != 1.23457e-10
(1e-06)] </P>
<H4>Example: test.cpp</H4>
<PRE class="code"><SPAN class="cpp-type">int</SPAN> test_main( <SPAN class="cpp-type">int</SPAN>, <SPAN class="cpp-type">char</SPAN>* [] ) {
<SPAN class="cpp-type">double</SPAN> v1 = <SPAN class="literal">4.1;</SPAN>
v1 = v1 * v1;
BOOST_CHECK_CLOSE( v1, <SPAN class="literal">16.81</SPAN>, <SPAN class="literal">1</SPAN>+<SPAN class="literal">2</SPAN> );
<SPAN class="comment">// 1(arithmetic operation) +
// 2(decimal to binary conversions) -
// number of rounding errors; should pass</SPAN>
<SPAN class="reserv-word">return</SPAN> <SPAN class="literal">0</SPAN>;
}</PRE>
<H4>Output:</H4>
<P class="test-output">&nbsp;</P>
<DIV class="see_also">
<H4>See Also</H4>
<P class="see_also_content"><A href="BOOST_CHECK_EQUAL.html" target="descr">BOOST_CHECK_EQUAL</A>,
<A href="../floating_point_comparison.html" target="_top">Floating point comparison algorithms</A></P>
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