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<h4 class="subsection">14.2.9 Floating-Point Conversions</h4>
<p>This section discusses the conversion specifications for floating-point
numbers: the ‘<samp><span class="samp">%f</span></samp>’, ‘<samp><span class="samp">%e</span></samp>’, ‘<samp><span class="samp">%E</span></samp>’, ‘<samp><span class="samp">%g</span></samp>’, and ‘<samp><span class="samp">%G</span></samp>’
conversions.
<p>The ‘<samp><span class="samp">%f</span></samp>’ conversion prints its argument in fixed-point notation,
producing output of the form
[<code>-</code>]<var>ddd</var><code>.</code><var>ddd</var><!-- /@w -->,
where the number of digits following the decimal point is controlled
by the precision you specify.
<p>The ‘<samp><span class="samp">%e</span></samp>’ conversion prints its argument in exponential notation,
producing output of the form
[<code>-</code>]<var>d</var><code>.</code><var>ddd</var><code>e</code>[<code>+</code>|<code>-</code>]<var>dd</var><!-- /@w -->.
Again, the number of digits following the decimal point is controlled by
the precision. The exponent always contains at least two digits. The
‘<samp><span class="samp">%E</span></samp>’ conversion is similar but the exponent is marked with the letter
‘<samp><span class="samp">E</span></samp>’ instead of ‘<samp><span class="samp">e</span></samp>’.
<p>The ‘<samp><span class="samp">%g</span></samp>’ and ‘<samp><span class="samp">%G</span></samp>’ conversions print the argument in the style
of ‘<samp><span class="samp">%e</span></samp>’ or ‘<samp><span class="samp">%E</span></samp>’ (respectively) if the exponent would be less
than -4 or greater than or equal to the precision; otherwise they use the
‘<samp><span class="samp">%f</span></samp>’ style. Trailing zeros are removed from the fractional portion
of the result and a decimal-point character appears only if it is
followed by a digit.
<p>The following flags can be used to modify the behavior:
<!-- Not @samp so we can have ` ' as an item. -->
<dl>
<dt>‘<samp><span class="samp">-</span></samp>’<dd>Left-justify the result in the field. Normally the result is
right-justified.
<br><dt>‘<samp><span class="samp">+</span></samp>’<dd>Always include a plus or minus sign in the result.
<br><dt>‘<samp> </samp>’<dd>If the result doesn't start with a plus or minus sign, prefix it with a
space instead. Since the ‘<samp><span class="samp">+</span></samp>’ flag ensures that the result includes
a sign, this flag is ignored if you supply both of them.
<br><dt>‘<samp><span class="samp">#</span></samp>’<dd>Specifies that the result should always include a decimal point, even
if no digits follow it. For the ‘<samp><span class="samp">%g</span></samp>’ and ‘<samp><span class="samp">%G</span></samp>’ conversions,
this also forces trailing zeros after the decimal point to be left
in place where they would otherwise be removed.
<br><dt>‘<samp><span class="samp">0</span></samp>’<dd>Pad the field with zeros instead of spaces; the zeros are placed
after any sign. This flag is ignored if the ‘<samp><span class="samp">-</span></samp>’ flag is also
specified.
</dl>
<p>The precision specifies how many digits follow the decimal-point
character for the ‘<samp><span class="samp">%f</span></samp>’, ‘<samp><span class="samp">%e</span></samp>’, and ‘<samp><span class="samp">%E</span></samp>’ conversions. For
these conversions, the default precision is <code>6</code>. If the precision
is explicitly <code>0</code>, this suppresses the decimal point character
entirely. For the ‘<samp><span class="samp">%g</span></samp>’ and ‘<samp><span class="samp">%G</span></samp>’ conversions, the precision
specifies how many significant digits to print. Significant digits are
the first digit before the decimal point, and all the digits after it.
If the precision is <code>0</code> or not specified for ‘<samp><span class="samp">%g</span></samp>’ or
‘<samp><span class="samp">%G</span></samp>’, it is treated like a value of <code>1</code>. If the value being
printed cannot be expressed precisely in the specified number of digits,
the value is rounded to the nearest number that fits.
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