Matters needing attention in numerical calculation in PHP

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One: rounded

1.round-rounding floating point numbers

Float round (float $val [, int $precision])

2:floor-rounding (rounding down)

Float floor (float $value)

3.ceil-one-in rounding (rounding up)

Float ceil (float $value)

Pit points: when the value is an integer, for example, 11, then floor (11) = 10, ceil (11) = 12; the problem is obvious, so pay special attention to this when calculating.

Solution: floor (11 + 0.01)

Two: multiplication and division of integers and decimals

This is true in the php world. If you use the +-* / of php to calculate floating-point numbers, you may encounter some incorrect results, such as echo intval (0.58-100). It prints 57 instead of 58, which is actually a bug in which floating-point numbers cannot be accurately represented by the underlying binary of the computer, which is cross-language, and I have the same problem with python. So basically most languages provide accurate computing class libraries or function libraries, such as php has a BC high-precision function library

The solution is to change the integer into a floating-point type 3.5x (float) 100 = 350.

Three: the weirdness of floating point numbers

Pothole: 8.50-8 = 0.500000001 actually the reason is similar to 2.

Solution: round () the result to improve the accuracy.

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