Bug #66959 [Ver]: bcadd with floats fails
Edit report at https://bugs.php.net/bug.php?id=66959&edit=1
ID: 66959
Updated by: cmb@php.net
Reported by: james dot turner dot phpninja at gmail dot com
Summary: bcadd with floats fails
Status: Verified
Type: Bug
Package: BC math related
Operating System: Ubuntu 13
PHP Version: 5.5.10
Block user comment: N
Private report: N
New Comment:
> Would be great if someone could make bcmath support scientific
> notation...
There would still be the issue that the string cast depends on the
locale, e.g.
<?php
setlocale(LC_NUMERIC, 'de_DE.UTF-8');
// ...
var_dump(bcadd(-0.05648055, -0.05648055, 8));
outputs
string(10) "0.00000000"
Previous Comments:
------------------------------------------------------------------------
[2014-04-02 22:04:09] trainmaster at gmx dot net
Some more examples (Output for 5.2.2 - 5.6.0alpha3):
var_dump(bcadd(0,-0.00555555,9));
// string(12) "-0.005555550"
var_dump((string) -0.00555555);
// string(11) "-0.00555555"
var_dump(bcadd(0,-0.00055555,9));
// string(12) "-0.000555550"
var_dump((string) -0.00055555);
// string(11) "-0.00055555"
var_dump(bcadd(0,-0.00005555,9));
// string(11) "0.000000000"
var_dump((string) -0.00005555);
// string(10) "-5.555E-05"
var_dump(bcadd(0,-0.00000555,9));
// string(11) "0.000000000"
var_dump((string) -0.00000555);
// string(9) "-5.55E-06"
var_dump(bcadd(0,-0.00000055,9));
// string(11) "0.000000000"
var_dump((string) -0.00000055);
// string(8) "-5.5E-07"
var_dump(bcadd(0,-0.00000005,9));
// string(11) "0.000000000"
var_dump((string) -0.00000005);
// string(6) "-5E-08"
------------------------------------------------------------------------
[2014-04-02 21:56:23] trainmaster at gmx dot net
@nikic
See bwoebi's example when string arguments are passed. The problem seems to be the scientific
notation.
------------------------------------------------------------------------
[2014-04-01 13:47:04] nikic@php.net
BCMath explicitly works with strings, not floating point numbers. In https://bugs.php.net/bug.php?id=55160 Mike made the
decision that we should not have extra support for passing floats to bc functions.
------------------------------------------------------------------------
[2014-04-01 13:17:45] bwoebi@php.net
Actually the bcmath extension doesn't like scientific notation.
var_dump((string)-0.00000545);
string(8) "-5.45E-6"
and
var_dump(bcadd("-0.05648055","-5.45E-6",9));
string(12) "-0.056480550"
------------
Would be great if someone could make bcmath support scientific notation...
------------------------------------------------------------------------
[2014-03-26 12:08:25] james dot turner dot phpninja at gmail dot com
Description:
------------
bcadd does not appear to work for certain numbers when using floats as inputs rather than strings.
This is particularly apparent if you json_decode from json to php variables where floats are
generated as you get floats not strings. Any attempt at casting to a string produces the same
output.
I can only assume it's actually an issue with float->string casting.
Test script:
---------------
$a = -0.05648055;
$b = -0.00000545;
$c = bcadd($a,$b,9);
$d = $a+$b;
echo $c; // => -0.05648055 <- WRONG
echo $d; // => -0.056486 <- CORRECT
assert($c == -0.056486);
Expected result:
----------------
assert ok
Usage of string literals for the negative floats works fine. However casting the floats to strings
fails (which is why I assume that bcadd also has the same problem in casting to strings before
computation).
Actual result:
--------------
assert fail
------------------------------------------------------------------------
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