Float double comparison Size Problem

I,

Comparing float and double types through ==,>,< will not cause compilation errors, but it is very likely to get incorrect results. This is because their memory distribution is different and cannot be compared directly. The correct method is to convert to the same type and compare the difference between the two. If the result is smaller than the specified small value, it is considered equal.

# Define EPS xxx

Const double EPS = xxx;

Xxx generally takes 1e-6.

Both of them can be used.

Then use

FABS (a-B) <EPS determines whether it is equal.

II,

1. Scope
The float and double ranges are determined by the number of digits of the index.
The float index has eight digits, while the double index has 11 digits. The distribution is as follows:
Float:
1bit (symbol bit) 8 bits (index bit) 23 bits (tail bit)
Double:
1bit (symbol bit) 11 bits (index bit) 52 bits (tail bit)
Therefore, the float index range is-127 ~ + 128, while the double index range is-1023 ~ + 1024, and the index bit is divided by complement code.
The negative index determines the smallest non-zero number of absolute values that floating point numbers can express. The positive index determines the maximum number of absolute values that floating point numbers can express, that is, the value range of floating point numbers.
Float range:-2 ^ 128 ~ + 2 ^ 128, that is,-3.40e + 38 ~ + 3.40e + 38; the double value range is-2 ^ 1024 ~ + 2 ^ 1024, that is,-1.79e + 308 ~ + 1.79e + 308.

2. Precision
The precision of float and double is determined by the number of digits of the ending number. Floating point numbers are stored in the memory in scientific notation, And the integer part is always an implicit "1". Since it remains unchanged, it cannot affect the accuracy.
Float: 2 ^ 23 = 8388608, a total of seven digits, which means that there can be a maximum of seven valid digits, but it is absolutely guaranteed to be 6 digits, that is, the float precision is 6 ~ 7 valid digits;
Double: 2 ^ 52 = 4503599627370496, a total of 16 digits. Similarly, the precision of double is 15 ~ 16 bits.

Float can have a maximum of seven digits.

The maximum number of valid digits of double is 16.