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<title>safe_signed_literal&lt;Value, PP , EP&gt; and safe_unsigned_literal&lt;Value, PP, EP&gt;</title>
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<td><h2>Safe Numerics</h2></td>
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<div class="titlepage"><div><div><h3 class="title">
<a name="safe_numerics.safe_literal"></a>safe_signed_literal&lt;Value, PP , EP&gt; and
  safe_unsigned_literal&lt;Value, PP, EP&gt;</h3></div></div></div>
<div class="toc"><dl class="toc">
<dt><span class="section"><a href="safe_literal.html#idm130203096240">Description</a></span></dt>
<dt><span class="section"><a href="safe_literal.html#idm130203094736">Model of</a></span></dt>
<dt><span class="section"><a href="safe_literal.html#idm130203090832">Associated Types</a></span></dt>
<dt><span class="section"><a href="safe_literal.html#idm130203083840">Template Parameters</a></span></dt>
<dt><span class="section"><a href="safe_literal.html#idm130203066304">Inherited Valid Expressions</a></span></dt>
<dt><span class="section"><a href="safe_literal.html#idm130203034032">Example of use</a></span></dt>
<dt><span class="section"><a href="safe_literal.html#safe_numerics.safe_literal.make_safe_literal"><code class="computeroutput">make_safe_literal(n, PP, EP) </code></a></span></dt>
<dt><span class="section"><a href="safe_literal.html#idm130203017088">Header</a></span></dt>
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<div class="titlepage"><div><div><h4 class="title">
<a name="idm130203096240"></a>Description</h4></div></div></div>
<p>A safe type which holds a literal value. This is required to be able
    to initialize other safe types in such a way that an exception code is not
    generated. It is also useful when creating constexpr versions of safe
    types. It contains one immutable value known at compile time and hence can
    be used in any constexpr expression.</p>
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<div class="titlepage"><div><div><h4 class="title">
<a name="idm130203094736"></a>Model of</h4></div></div></div>
<p><a class="link" href="numeric.html" title="Numeric&lt;T&gt;">Integer</a></p>
<p><a class="link" href="safe_numeric_concept.html" title="SafeNumeric&lt;T&gt;">SafeNumeric</a></p>
<p>This type inherits all the notation, associated types and template
    parameters and valid expressions of <a class="link" href="safe_numeric_concept.html" title="SafeNumeric&lt;T&gt;">SafeNumeric</a> types. The
    following specify additional features of this type.</p>
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<a name="idm130203090832"></a>Associated Types</h4></div></div></div>
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<td align="left"><code class="computeroutput">PP</code></td>
<td align="left">A type which specifies the result type of an expression
            using safe types.</td>
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<td align="left"><code class="computeroutput">EP</code></td>
<td align="left">A type containing members which are called when a correct
            result cannot be returned</td>
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<div class="titlepage"><div><div><h4 class="title">
<a name="idm130203083840"></a>Template Parameters</h4></div></div></div>
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<th align="left">Parameter</th>
<th align="left">Type Requirements</th>
<th align="left">Description</th>
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<td align="left"><code class="computeroutput">Value</code></td>
<td align="left"><code class="computeroutput"><a class="link" href="numeric.html" title="Numeric&lt;T&gt;">Integer</a></code></td>
<td align="left">value used to initialize the literal</td>
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<td align="left"><code class="computeroutput">PP</code></td>
<td align="left"><a class="link" href="numeric.html" title="Numeric&lt;T&gt;">PromotionPolicy&lt;PP&gt;</a></td>
<td align="left"><p>Optional promotion policy. Default value is
            <code class="computeroutput">void</code></p></td>
</tr>
<tr>
<td align="left"><code class="computeroutput">EP</code></td>
<td align="left"><a class="link" href="numeric.html" title="Numeric&lt;T&gt;">Exception
            Policy&lt;EP&gt;</a></td>
<td align="left"><p>Optional exception policy. Default value is
            <code class="computeroutput">void</code></p></td>
</tr>
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<div class="titlepage"><div><div><h4 class="title">
<a name="idm130203066304"></a>Inherited Valid Expressions</h4></div></div></div>
<p>safe literal types are immutable. Hence they only inherit those
    valid expressions which don't change the value. <span class="emphasis"><em>This excludes
    assignment, increment, and decrement and all unary operators except unary
    -, + and ~</em></span>. Other than that, they can be used anywhere a <a class="link" href="safe_numeric_concept.html" title="SafeNumeric&lt;T&gt;">SafeNumeric</a> type can
    be used. Note that the default promotion and exception policies are void.
    This is usually convenient since when a safe literal is used in a binary
    operation, this will inherit the policies of the other type. On the other
    hand, this can be inconvenient when operands of a binary expression are
    both safe literals. This will fail to compile since there are no
    designated promotion and exception policies. The way to address this to
    assign specific policies as in this example.</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">&gt;</span>
<span class="keyword">using</span> <span class="identifier">compile_time_value</span> <span class="special">=</span> <span class="identifier">safe_signed_literal</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span><span class="special">;</span>

<span class="keyword">constexpr</span> <span class="identifier">compile_time_value</span><span class="special">&lt;</span><span class="number">1000</span><span class="special">&gt;</span> <span class="identifier">x</span><span class="special">;</span>
<span class="keyword">constexpr</span> <span class="identifier">compile_time_value</span><span class="special">&lt;</span><span class="number">0</span><span class="special">&gt;</span> <span class="identifier">y</span><span class="special">;</span>

<span class="comment">// should compile and execute without problem</span>
    
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">x</span> <span class="special">&lt;&lt;</span> <span class="char">'\n'</span><span class="special">;</span>

<span class="comment">// all the following statements should fail to compile because there are </span>
<span class="comment">// no promotion and exception policies specified.</span>
<span class="keyword">constexpr</span> <span class="identifier">safe</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">z</span> <span class="special">=</span> <span class="identifier">x</span> <span class="special">/</span> <span class="identifier">y</span><span class="special">;</span>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="idm130203034032"></a>Example of use</h4></div></div></div>
<pre class="programlisting"><a href="../../include/safe_integer_literal.hpp" target="_top"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">numeric</span><span class="special">/</span><span class="identifier">safe_numerics</span><span class="special">/</span><span class="identifier">safe_integer_literal</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></a>

<span class="keyword">constexpr</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">numeric</span><span class="special">::</span><span class="identifier">safe_signed_literal</span><span class="special">&lt;</span><span class="number">42</span><span class="special">&gt;</span> <span class="identifier">x</span><span class="special">;</span>
</pre>
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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="safe_numerics.safe_literal.make_safe_literal"></a><code class="computeroutput">make_safe_literal(n, PP, EP) </code>
</h4></div></div></div>
<p>This is a macro which returns an instance of a safe literal type.
    This instance will hold the value n. The type of the value returned will
    be the smallest safe type which can hold the value <code class="computeroutput">n</code>.</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="idm130203017088"></a>Header</h4></div></div></div>
<p><a href="../../include/safe_integer_literal.hpp" target="_top">#include
    &lt;boost/numeric/safe_numerics/safe_integer_literal.hpp&gt;</a></p>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2012-2018 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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