Bug #75558 [Nab]: Float to integer conversion
Edit report at https://bugs.php.net/bug.php?id=75558&edit=1
ID: 75558
User updated by: cyrille dot php at giquello dot fr
Reported by: cyrille dot php at giquello dot fr
Summary: Float to integer conversion
Status: Not a bug
Type: Bug
Package: *General Issues
Operating System: Ubuntu 16.04
PHP Version: 7.1.11
Block user comment: N
Private report: N
New Comment:
Thanks à lot @nikic
And sorry for noise.
Previous Comments:
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[2017-11-23 11:28:35] nikic@php.net
@cyrille: The reason it "works" in Java is that you're using the float type instead
of the double type. If you use the double type instead, you will receive 61943 as the result.
Floating-point numbers in PHP are always double-precision, not single-precision.
@rhsoft: Floating-point to string conversion is controlled by the "precision" ini
settings. If you would like to see all round-trip relevant digits, set precision=-1. In this case,
this will display "61943.99999999999" rather than "61944".
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[2017-11-23 11:17:43] cyrille dot php at giquello dot fr
In Java
float a = (float) (103.24 * 6 * Math.pow(10,2)) ;
System.out.println( a ); // print 61944.0
System.out.println( (int) a ); // print 61944, not 61943
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[2017-11-23 11:15:03] cyrille dot php at giquello dot fr
I do not want to round() but only truncate decimal part, if one exists.
You're example well show that integer casting make lost one unit on a number without decimal :
php > echo (int)( 103.24 * 6 * 10**2);
61943
Perhaps it's not a bug, I've just to learn the well use of float.
Thanks for your answer.
Cheers.
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[2017-11-23 11:06:20] spam2 at rhsoft dot net
> If you don't want truncating conversion
where are the decimal parts which could be truncated?
php > echo 103.24 * 6 * 10**2;
61944
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[2017-11-23 11:03:21] nikic@php.net
I have no idea what you tried in Python and Java, but it was clearly something else, because these
are standard floating point semantics that are consistent across all languages. I've just
checked (int)(103.24 * 6 * 10**2) on Python 3.6 and it indeed gives 61943, as expected.
If you don't want truncating conversion ("round down" for positive numbers),
don't use integer casts, or ensure that the floating point number represents an exact integer
beforehand, by using round().
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