How to solve the accuracy problem of C++ floating-point comparison

This article mainly introduces "how to solve the accuracy problem of C++ floating point comparison". In daily operation, I believe many people have doubts about how to solve the accuracy problem of C++ floating point comparison. The editor consulted all kinds of data and sorted out simple and easy-to-use methods of operation. I hope it will be helpful to answer the doubt of "how to solve the accuracy problem of C++ floating point comparison". Next, please follow the editor to study!

1 introduction

Let me give you an example:

# include

Int main ()

{

Float a = 0.1

Float b = 0.2

Float c = a + b

If (c = = 0.3) {

Printf ("c = = 0.3\ n")

} else {

Printf ("0.1 + 0.2! = 0.3\ n")

}

Return 0

}

C! = 0.3

A _

If the variables a, b for 0.75, 0.5, you can see that the run c = = 1.25, which means that the floating-point operation is unstable.

A quarter of a century, a quarter of a century, a circle of 0.75, a circle of 1.25.

Why it can be good and bad, because not all decimals can be represented by the floating point standard (IEEE 754).

Therefore, judging whether two floating-point variables are equal cannot be simply achieved by the "= =" operator. When floating-point numbers are compared, the difference between them is generally within a certain range.

Bool feq (float a float b) {

Return fabs (afort b)