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- Some Double -> float's

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- Some extra notes


git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@53773 c90b9560-bf6c-de11-be94-00142212c4b1
This commit is contained in:
Jeroen van Wolffelaar 2001-08-07 22:40:53 +00:00
parent 5684d889a8
commit 98c6b554cf
1 changed files with 24 additions and 22 deletions
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46
language/types.xml
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@ -1,4 +1,4 @@
<!-- $Revision: 1.42 $ -->
<!-- $Revision: 1.43 $ -->
<chapter id="language.types">
<title>Types</title>
@ -29,7 +29,7 @@
<listitem>
<simpara>
<link linkend="language.types.double">floating-point number (double)</link>
<link linkend="language.types.double">floating-point number (float)</link>
</simpara>
</listitem>
@ -92,7 +92,7 @@
<simpara>
In parameter definitions you can also encounter the 'number' pseudo-type,
that indicates a parameter that is either <type>integer</type> or
<type>double</type>.
<type>float</type>.
</simpara>
-->
</note>
@ -202,7 +202,7 @@ if ($show_separators)
> 0 (zero) </simpara>
</listitem>
<listitem>
<simpara>the <link linkend="language.types.double">double</link>
<simpara>the <link linkend="language.types.double">float</link>
0.0 (zero) </simpara>
</listitem>
<listitem>
@ -292,12 +292,13 @@ $a = 0x1A; # hexadecimal number (equivalent to 26 decimal)
-->
The size of an integer is platform-dependent, although a
maximum value of about two billion is the usual value
(that's 32 bits signed).
(that's 32 bits signed). PHP does not support unsigned
integers.
</para>
<note><!-- or warning? -->
<simpara>
In PHP there is no such thing as integer division. <literal>1/2</literal>
yields the <type>double</type> <literal>0.5</literal>. <!-- See
yields the <type>float</type> <literal>0.5</literal>. <!-- See
??? for more information. (with the operators, or with type-jug) -->
</simpara>
</note>
@ -307,7 +308,7 @@ $a = 0x1A; # hexadecimal number (equivalent to 26 decimal)
<title>Integer overflow</title>
<para>
If you specify a number beyond the bounds of the <type>integer</type>-type,
it will be interpreted as a <type>double</type> instead.
it will be interpreted as a <type>float</type> instead.
<informalexample>
<programlisting role="php">
$large_number = 2147483647;
@ -315,18 +316,18 @@ var_dump($large_number);
// output: int(2147483647)
$large_number = 2147483648;
var_dump($large_number);
// output: float(2147483648) <!--
// output: float(2147483648)
php is inconsistent here...
vardump says float, gettype says double
// this goes also for hexadecimal specified integers:
-->
var_dump( 0x80000000 );
// output: float(2147483648)
</programlisting>
</informalexample>
Furthermore, if some function or operator yields a number that is beyond
the boundaries of <type>integer</type>, it will also
be automatically converted to
<type>double</type>.
<type>float</type>.
<informalexample>
<programlisting role="php">
$million = 1000000;
@ -373,7 +374,7 @@ var_dump($large_number);
</simpara>
</sect3>
<sect3 id="language.types.integer.casting.from-double">
<sect3 id="language.types.integer.casting.from-float">
<title>From <link linkend="language.types.double">floating point numbers</link></title>
<simpara>
When converting from float to integer, the number will
@ -443,7 +444,7 @@ echo (int) ( (0.1+0.7) * 10 ); // echoes 7!
<sect1 id="language.types.double">
<title>Floating point numbers</title>
<para>
Floating point numbers (AKA "doubles", "floats" or "real numbers") can be
Floating point numbers (AKA "floats", "doubles" or "real numbers") can be
specified using any of the following syntaxes:
<synopsis>
$a = 1.234; $a = 1.2e3; $a = 7E-10;
@ -455,7 +456,7 @@ DNUM ([0-9]*[\.][0-9]+)|([0-9]+[\.][0-9]*)
EXPONENT_DNUM (({LNUM}|{DNUM})[eE][+-]?{LNUM})
-->
The size of a floating point number is platform-dependent,
The size of a float is platform-dependent,
although a maximum of ~1.8e308 with a precision of roughly 14
decimal digits is a common value (that's 64 bit IEEE format).
</para>
@ -942,7 +943,7 @@ $last = $str{strlen($str)-1};
value and type are determined as follows.
</simpara>
<simpara>
The string will evaluate as a double if it contains any of the
The string will evaluate as a <type>float</type> if it contains any of the
characters '.', 'e', or 'E'. Otherwise, it will evaluate as an
integer.
</simpara>
@ -1752,9 +1753,9 @@ $var = Null;
</simpara>
<para>
An example of PHP's automatic type conversion is the addition
operator '+'. If any of the operands is a double, then all
operands are evaluated as doubles, and the result will be a
double. Otherwise, the operands will be interpreted as integers,
operator '+'. If any of the operands is a float, then all
operands are evaluated as floats, and the result will be a
float. Otherwise, the operands will be interpreted as integers,
and the result will also be an integer. Note that this does NOT
change the types of the operands themselves; the only change is in
how the operands are evaluated.
@ -1765,7 +1766,7 @@ $foo = "0"; // $foo is string (ASCII 48)
$foo++; // $foo is the string "1" (ASCII 49)
-->
$foo += 2; // $foo is now an integer (2)
$foo = $foo + 1.3; // $foo is now a double (3.3)
$foo = $foo + 1.3; // $foo is now a float (3.3)
$foo = 5 + "10 Little Piggies"; // $foo is integer (15)
$foo = 5 + "10 Small Pigs"; // $foo is integer (15)
<!--
@ -1849,7 +1850,7 @@ $a[0] = "f"; // What about string offsets? What happens?
<informalexample>
<programlisting role="php">
$foo = 10; // $foo is an integer
$bar = (double) $foo; // $bar is a double
$bar = (float) $foo; // $bar is a float
</programlisting>
</informalexample>
</para>
@ -1863,7 +1864,7 @@ $bar = (double) $foo; // $bar is a double
<simpara>(bool), (boolean) - cast to boolean</simpara>
</listitem>
<listitem>
<simpara>(real), (double), (float) - cast to double</simpara>
<simpara>(float), (double), (real) - cast to float</simpara>
</listitem>
<listitem>
<simpara>(string) - cast to string</simpara>
@ -1993,4 +1994,5 @@ sgml-exposed-tags:nil
sgml-local-catalogs:nil
sgml-local-ecat-files:nil
End:
vim: ts=1 sw=1 et syntax=sgml
-->