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<a name="mpfr-conversion-functions"></a>
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<a name="mpfr-conversion-functions-1"></a>
<h3 class="subsection">D.14.8 <code>mpfr</code> conversion functions</h3>

<p>The functions described in this section convert between <code>mpfr</code>
numbers and character strings, naturals, or standard IEEE floating
point format (in their list representations). Where these functions
have similar or equivalent counterparts in the <code>mpfr</code> library&rsquo;s
native API, the names have been changed for mnemonic reasons.
</p>
<dl compact="compact">
<dt> <code>dbl2mp</code></dt>
<dd><p>The input is a standard floating point number as in <a href="math.html#math"><code>math</code></a>. The
result is an <code>mpfr</code> number equal to the input with a
fixed precision, currently set to 160 bits.
</p></dd>
<dt> <code>mp2dbl</code></dt>
<dd><p>The input is an <code>mpfr</code> number, and the output is the best
possible approximation to it by a standard a double precision
number.
</p></dd>
<dt> <code>str2mp</code></dt>
<dd><p>The input is a pair <code>(<var>prec</var>,<var>s</var>)</code>, where <var>prec</var> is a
natural number specifying the precision, and <var>s</var> is a string
expressing a floating point number in C format. The output is an
<code>mpfr</code> number with the specified precision.
</p></dd>
<dt> <code>mp2str</code></dt>
<dd><p>The input is an <code>mpfr</code> number, and the output is a character
string expressing the number in exponential decimal notation.
Sufficiently many decimal digits are included in the string to express
the full precision.
</p></dd>
<dt> <code>nat2mp</code></dt>
<dd><p>The input is a natural number represented as described in
<a href="Representation-of-Numeric-and-Textual-Data.html#Representation-of-Numeric-and-Textual-Data">Representation of Numeric and Textual Data</a>,
and the output is an <code>mpfr</code> number of sufficient precision to
express the natural number exactly.
</p></dd>
</dl>

<p>The <code>mp2str</code> function enhances the native <code>mpfr_get_str</code>
function by properly formatting the output string rather than only
listing the digits of the mantissa.
</p>
<p>The <code>nat2mp</code> function does not rely on the <code>mpfr</code> native
integer conversion functions, so natural numbers with any number of
bits up to <code>MP_PREC_MAX</code> can be used losslessly. There is
currently no conversion in the other direction.
</p>
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