PHP8 function: Precision calculation skills of fdiv()

PHP8 is the latest PHP language version, which introduces many exciting new features and improvements. One of them is the fdiv() function, which can be used to accurately calculate the division operation of floating point numbers.

In previous PHP versions, using the basic division operator (/) could cause precision issues. This is because when calculating floating point numbers, the computer needs to convert the number into binary format in order to perform the calculation. However, some numbers cannot be accurately represented as binary, which leads to some precision issues. For example, using the division operator to calculate the result of dividing 10 by 3 might result in 3.3333333333333 instead of exactly 3.3333333333333335.

The fdiv() function avoids these precision issues by using precise floating-point arithmetic as defined in the IEEE 754 standard. It can perform division operations without losing any precision and return an exact result. For example, using the fdiv(10, 3) function call, will return 3.3333333333333335, which is an exact result.

However, to use the fdiv() function correctly, you need to know a few tricks:

1. Avoid using simple divisors. If you use a simple divisor (such as 2 or 10), then the advantages of the fdiv() function will become negligible. This is because these divisors can be accurately represented as binary numbers. So for these cases, using the division operator might be a better choice.
2. Use enough digits. By default, the fdiv() function uses 53 bits of precision for calculations. This means it can provide adequate accuracy in most situations. However, if you require higher precision results, you can achieve this by setting the number of bits to a higher value. For example, using the fdiv(10, 3, 64) function call will return a 64-bit accurate result.
3. Handling infinites and NaNs. If you try to divide a number by 0, or an infinite number by an infinite number, or NaN (which is not a number) by another number, the fdiv() function will return NaN. Therefore, you need to be aware of these special cases when using the fdiv() function for calculations.
4. Understand rounding rules. The fdiv() function uses the "nearest even" rounding rule. This means that if the last digit of the result is 5, then it will be rounded to the nearest even number (for example, 4 or 6). This rounding rule is designed to provide the best accuracy and predictability in all situations.

To sum up, the fdiv() function is a very useful tool that can help you avoid precision problems in floating point division operations. To use it correctly, you need to know the above tips and understand its limitations. If you need to perform high-precision floating point calculations, the fdiv() function may be one of your best choices.

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