golang float to string

Go language is a relatively young programming language. Due to its simplicity, efficiency and security, it is increasingly popular among programmers and is widely used in Web applications, network programming, cloud computing, big data and other fields. . In the Go language, float type data is often used to represent decimals and floating point values. When we need to convert float type data into string type, we need to use some related functions.

1. Function Float64Tostring in the strconv package
   In the Go language, you can use the "FormatFloat" function of the "strconv" package to convert a 64-bit floating point real number into a string, and also You can specify the conversion format, such as retaining n digits after the decimal point, exponential notation, etc.

Function signature: func FormatFloat(f float64, fmt byte, prec, bitSize int) string

Among them, the parameter f is the floating point number to be converted, and fmt represents the conversion format, ' f' represents decimal representation, 'e' represents scientific notation, 'E' represents scientific notation, prec represents the precision after the decimal point, and bitSize represents the number of digits of the numerical type (32 or 64 bits).

Sample code:

package main

import "fmt"
import "strconv"

func main() {

num := 3.141592654
str := strconv.FormatFloat(num, 'f', 2, 64)
fmt.Println("转换后的字符串为：", str)

}

Output:

The converted string is: 3.14

In this example, we convert the floating point number 3.141592654 into a character with a precision of 2 string and output the result. The output result at this time is 3.14.

2. Use the fmt.Sprintf function directly
   When writing code, we can also use the fmt.Sprintf function to convert a float type to a string type. The %f placeholder is used in the format string of this function to represent the output of float type data.

Sample code:

package main

import "fmt"

func main() {

num := 1.61803398875
str := fmt.Sprintf("%f", num)
fmt.Println(str)

}

Output:

1.618034

In this example, we convert the floating point number 1.61803398875 into a string type using the fmt.Sprintf function and output the result. The result is the same as the default format for float64 values.

3. strconv.FormatFloat() is used in combination with strconv.AppendFloat()
   If you need to convert the float64 type to a string type, you need to consider the storage of the string. In order to improve the character To improve string processing speed, you can use strconv.AppendFloat() to avoid some string copying and appending operations. Some understanding is required here:

The returned []byte type is used as the next fillable position of w. To avoid memory allocation, call w.Grow(n) ahead of time, where n is the total number of bytes to write or the maximum number width 1 (i.e. the combination of the total number width with good alignment and adding a decimal point)

w is an instance that implements io.Writer. The string representation of

fn is based on the format fmt, with prec decimal places (-1 means using the fewest digits). In particular, the following format descriptors %v and %e both result in scientific notation here. The smallest number guaranteed to be reversible by a floating point constant can be obtained using Float32bits (-1<<31) and Float64bits (-1<<63).

The non-numeric behavior of f values ​​is exactly the same as fmt.Fprintf.

Sample code:

package main

import "strconv"

func main() {

num := 3.141592653
b := make([]byte, 0, 64)
b = strconv.AppendFloat(b, num, 'f', -1, 64)

}

In this example, we converted the floating point number 3.141592653 into a string type and stored it in the []byte type variable b. It should be noted that the number of decimal places at this time is -1, that is, the minimum number of digits is used to represent the value.

If you want to accurately control the float-to-string algorithm, you can learn about the Golang standard library math/big.

Summary:
In the Go language, there are three main ways to convert float type data to string type data: using the fmt.FormatFloat function in the strconv package, using the fmt.Sprintf function, and using strconv. FormatFloat() is used in combination with strconv.AppendFloat(). You can customize the formatting using the functions in the strconv package. It is convenient and simple to use the fmt.Sprintf function. The combination of strconv.FormatFloat() and strconv.AppendFloat() can reduce string copying and appending operations and improve string processing speed. It should be noted that during precision calculation and use, care should be taken to avoid errors caused by floating point number conversion, especially floating point numbers with a larger range.

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