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| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="boost_multiprecision.tut.limits.how_to_tell"></a><a class="link" href="how_to_tell.html" title="How to Determine the Kind of a Number From std::numeric_limits">How to |
| Determine the Kind of a Number From <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span></code></a> |
| </h4></div></div></div> |
| <p> |
| Based on the information above, one can see that different kinds of numbers |
| can be differentiated based on the information stored in <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span></code>. This is in addition to |
| the traits class <a class="link" href="../../ref/number.html#boost_multiprecision.ref.number.traits_class_support">number_category</a> |
| provided by this library. |
| </p> |
| <h5> |
| <a name="boost_multiprecision.tut.limits.how_to_tell.h0"></a> |
| <span class="phrase"><a name="boost_multiprecision.tut.limits.how_to_tell.integer_types"></a></span><a class="link" href="how_to_tell.html#boost_multiprecision.tut.limits.how_to_tell.integer_types">Integer |
| Types</a> |
| </h5> |
| <p> |
| For an integer type T, all of the following conditions hold: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_specialized</span> <span class="special">==</span> <span class="keyword">true</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_integer</span> <span class="special">==</span> <span class="keyword">true</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_exact</span> <span class="special">==</span> <span class="keyword">true</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">min_exponent</span> <span class="special">==</span> <span class="number">0</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">max_exponent</span> <span class="special">==</span> <span class="number">0</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">min_exponent10</span> <span class="special">==</span> <span class="number">0</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">max_exponent10</span> <span class="special">==</span> <span class="number">0</span> |
| </pre> |
| <p> |
| In addition the type is <span class="emphasis"><em>signed</em></span> if: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_signed</span> <span class="special">==</span> <span class="keyword">true</span> |
| </pre> |
| <p> |
| If the type is arbitrary precision then: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_bounded</span> <span class="special">==</span> <span class="keyword">false</span> |
| </pre> |
| <p> |
| Otherwise the type is bounded, and returns a non zero value from: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">max</span><span class="special">()</span> |
| </pre> |
| <p> |
| and has: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_modulo</span> <span class="special">==</span> <span class="keyword">true</span> |
| </pre> |
| <p> |
| if the type implements modulo arithmetic on overflow. |
| </p> |
| <h5> |
| <a name="boost_multiprecision.tut.limits.how_to_tell.h1"></a> |
| <span class="phrase"><a name="boost_multiprecision.tut.limits.how_to_tell.rational_types"></a></span><a class="link" href="how_to_tell.html#boost_multiprecision.tut.limits.how_to_tell.rational_types">Rational |
| Types</a> |
| </h5> |
| <p> |
| Rational types are just like integers except that: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_integer</span> <span class="special">==</span> <span class="keyword">false</span> |
| </pre> |
| <h5> |
| <a name="boost_multiprecision.tut.limits.how_to_tell.h2"></a> |
| <span class="phrase"><a name="boost_multiprecision.tut.limits.how_to_tell.fixed_precision_types"></a></span><a class="link" href="how_to_tell.html#boost_multiprecision.tut.limits.how_to_tell.fixed_precision_types">Fixed |
| Precision Types</a> |
| </h5> |
| <p> |
| There appears to be no way to tell these apart from rational types, unless |
| they set: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_exact</span> <span class="special">==</span> <span class="keyword">false</span> |
| </pre> |
| <p> |
| This is because these types are in essence a rational type with a fixed |
| denominator. |
| </p> |
| <h5> |
| <a name="boost_multiprecision.tut.limits.how_to_tell.h3"></a> |
| <span class="phrase"><a name="boost_multiprecision.tut.limits.how_to_tell.floating_point_types"></a></span><a class="link" href="how_to_tell.html#boost_multiprecision.tut.limits.how_to_tell.floating_point_types">Floating |
| Point Types</a> |
| </h5> |
| <p> |
| For a floating point type T, all of the following conditions hold: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_specialized</span> <span class="special">==</span> <span class="keyword">true</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_integer</span> <span class="special">==</span> <span class="keyword">false</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_exact</span> <span class="special">==</span> <span class="keyword">false</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">min_exponent</span> <span class="special">!=</span> <span class="number">0</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">max_exponent</span> <span class="special">!=</span> <span class="number">0</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">min_exponent10</span> <span class="special">!=</span> <span class="number">0</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">max_exponent10</span> <span class="special">!=</span> <span class="number">0</span> |
| </pre> |
| <p> |
| In addition the type is <span class="emphasis"><em>signed</em></span> if: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_signed</span> <span class="special">==</span> <span class="keyword">true</span> |
| </pre> |
| <p> |
| And the type may be decimal or binary depending on the value of: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">radix</span> |
| </pre> |
| <p> |
| In general, there are no arbitrary precision floating point types, and |
| so: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_bounded</span> <span class="special">==</span> <span class="keyword">false</span> |
| </pre> |
| <h5> |
| <a name="boost_multiprecision.tut.limits.how_to_tell.h4"></a> |
| <span class="phrase"><a name="boost_multiprecision.tut.limits.how_to_tell.exact_floating_point_types"></a></span><a class="link" href="how_to_tell.html#boost_multiprecision.tut.limits.how_to_tell.exact_floating_point_types">Exact |
| Floating Point Types</a> |
| </h5> |
| <p> |
| Exact floating point types are a <a href="http://en.wikipedia.org/wiki/Field_%28mathematics%29" target="_top">field</a> |
| composed of an arbitrary precision integer scaled by an exponent. Such |
| types have no division operator and are the same as floating point types |
| except: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_exact</span> <span class="special">==</span> <span class="keyword">true</span> |
| </pre> |
| <h5> |
| <a name="boost_multiprecision.tut.limits.how_to_tell.h5"></a> |
| <span class="phrase"><a name="boost_multiprecision.tut.limits.how_to_tell.complex_numbers"></a></span><a class="link" href="how_to_tell.html#boost_multiprecision.tut.limits.how_to_tell.complex_numbers">Complex |
| Numbers</a> |
| </h5> |
| <p> |
| For historical reasons, complex numbers do not specialize <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span></code>, instead you must inspect |
| <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">></span></code>. |
| </p> |
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| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
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