PHP floating point calculation problem

If you use PHP's +-*/ to calculate floating point numbers, you may encounter some problems with incorrect calculation results. For example, echo intval(0.58*100); will print 57 instead of 58. This is actually due to the inability of the underlying binary system of the computer. A bug in accurately representing floating point numbers

is cross-language. I also encountered this problem using python. So basically most languages ​​provide class libraries or function libraries for precise calculations. For example, PHP has a BC high-precision function library. Here are some commonly used BC high-precision functions.

php BC high-precision function library includes: addition, comparison, division, subtraction, remainder, multiplication, nth power, configure the default number of decimal points, and square. These functions are more useful when it comes to monetary calculations, such as e-commerce price calculations.

/**

* Compare two high-precision numbers

*

* @access global

* @param float $left

* @param float $right

* @param int $scale The number of decimal places to be accurate

*

* @return int $left==$right returns 0 | $left$right returns 1

*/

var_dump(bccomp($left=4.45, $right=5.54, 2));

// -1

/**

* Add two high-precision numbers

*

* @access global

* @param float $left

* @param float $right

* @param int $scale The number of decimal places to be accurate

*

* @return string

*/

var_dump(bcadd($left=1.0321456, $right=0.0243456, 2));

//1.04

/**

* Subtract two high-precision numbers

*

* @access global

* @param float $left

* @param float $right

* @param int $scale The number of decimal places to be accurate

*

* @return string

*/

var_dump(bcsub($left=1.0321456, $right=3.0123456, 2));

//-1.98

/**

* Divide two high-precision numbers

*

* @access global

* @param float $left

* @param float $right

* @param int $scale The number of decimal places to be accurate

*

* @return string

*/

var_dump(bcdiv($left=6, $right=5, 2));

/ /1.20

/**

* Multiply two high-precision numbers

*

* @access global

* @param float $left

* @param float $right

* @param int $scale The number of decimal places to be accurate

*

* @return string

*/

var_dump(bcmul($left=3.1415926, $right=2.4569874566, 2));

//7.71

/**

* Set the number of decimal points for the bc function

*

* @access global

* @param int $scale The number of decimal points to be accurate

*

* @return void

* /

bcscale(3);

var_dump(bcdiv('105', '6.55957'));

// 16.007

Note: Regarding the number of digits set, the excess is discarded, not Rounding