language/types/float.xml
e587d0655e426f97b3fcb431453da5030e743b23
e587d0655e426f97b3fcb431453da5030e743b23
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@@ -29,7 +29,7 @@ $d = 1_234.567; // as of PHP 7.4.0
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<programlisting>
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<![CDATA[
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LNUM [0-9]+(_[0-9]+)*
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DNUM ([0-9]*(_[0-9]+)*[\.]{LNUM}) | ({LNUM}[\.][0-9]*(_[0-9]+)*)
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DNUM ({LNUM}?"."{LNUM}) | ({LNUM}"."{LNUM}?)
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EXPONENT_DNUM (({LNUM} | {DNUM}) [eE][+-]? {LNUM})
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]]>
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</programlisting>
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@@ -82,17 +82,36 @@ EXPONENT_DNUM (({LNUM} | {DNUM}) [eE][+-]? {LNUM})
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<sect2 xml:id="language.types.float.casting">
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<title>Converting to float</title>
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<para>
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For information on converting <type>string</type>s to <type>float</type>, see
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<link linkend="language.types.string.conversion">String conversion to
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numbers</link>. For values of other types, the conversion is performed by
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converting the value to <type>integer</type> first and then to
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<type>float</type>. See
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<link linkend="language.types.integer.casting">Converting to integer</link>
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for more information. As of PHP 5, a notice is thrown if an
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<type>object</type> is converted to <type>float</type>.
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</para>
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<sect3 xml:id="language.types.float.casting.from-string">
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<title>From strings</title>
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<simpara>
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If the string is
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<link linkend="language.types.numeric-strings">numeric</link>
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or leading numeric then it will resolve to the
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corresponding float value, otherwise it is converted to zero
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(<literal>0</literal>).
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</simpara>
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</sect3>
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<sect3 xml:id="language.types.float.casting.from-other">
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<title>From other types</title>
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<para>
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For values of other types, the conversion is performed by converting the
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value to <type>int</type> first and then to <type>float</type>. See
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<link linkend="language.types.integer.casting">Converting to integer</link>
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for more information.
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</para>
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<note>
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<para>
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As certain types have undefined behavior when converting to
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<type>int</type>, this is also the case when converting to
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<type>float</type>.
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</para>
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</note>
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</sect3>
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</sect2>
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<sect2 xml:id="language.types.float.comparison">
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or unit roundoff, and is the smallest acceptable difference in calculations.
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</para>
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<informalexample>
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<simpara>
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<varname>$a</varname> and <varname>$b</varname> are equal to 5 digits of
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precision.
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</simpara>
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<para>
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<varname>$a</varname> and <varname>$b</varname> are equal to 5 digits of
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precision.
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</para>
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<example>
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<title>Comparing Floats</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$b = 1.23456780;
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$epsilon = 0.00001;
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if(abs($a-$b) < $epsilon) {
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if (abs($a - $b) < $epsilon) {
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echo "true";
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}
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?>
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]]>
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</programlisting>
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</informalexample>
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</example>
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</sect2>
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<sect2 xml:id="language.types.float.nan">
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