Float64 类型打印为 Golang 中的 int

Question

令人惊讶的是，我找不到其他人遇到同样的问题；我尝试简单地在 Go 中初始化一个 float64 并打印它，然后尝试进行字符串转换并打印它。两种输出都不准确。

我已经用很多分数尝试过这个，包括那些不解析为重复小数的分数，以及简单地写出浮点数和打印（例如 num := 1.5 然后 fmt.Println(num) 给出输出1).

package main

import (
    "fmt"
    "strconv"
)

func main() {
    var num float64
    num = 5/3
    fmt.Printf("%v\n", num)
    numString := strconv.FormatFloat(num, 'f', -1, 64)
    fmt.Println(numString)
}

预期：

// Output:
1.66
1.66

实际：

// Output:
1
1

Answer 1

The Go Programming Language Specification

Integer literals

An integer literal is a sequence of digits representing an integer constant.

Floating-point literals

A floating-point literal is a decimal representation of a floating-point constant. It has an integer part, a decimal point, a fractional part, and an exponent part. The integer and fractional part comprise decimal digits; the exponent part is an e or E followed by an optionally signed decimal exponent. One of the integer part or the fractional part may be elided; one of the decimal point or the exponent may be elided.

Arithmetic operators

For two integer values x and y, the integer quotient q = x / y and remainder r = x % y satisfy the following relationships:
x = q*y + r  and  |r| < |y|
with x / y truncated towards zero.

您使用整数文字和算术（x / y 截断为零）写道：

package main

import (
    "fmt"
    "strconv"
)

func main() {
    var num float64
    num = 5 / 3 // float64(int(5)/int(3))
    fmt.Printf("%v\n", num)
    numString := strconv.FormatFloat(num, 'f', -1, 64)
    fmt.Println(numString)
}

游乐场：https://play.golang.org/p/PBqSbpHvuSL

输出：

1
1

你应该使用 floating-point 文字和算术来写：

package main

import (
    "fmt"
    "strconv"
)

func main() {
    var num float64
    num = 5.0 / 3.0 // float64(float64(5.0) / float64 (3.0))
    fmt.Printf("%v\n", num)
    numString := strconv.FormatFloat(num, 'f', -1, 64)
    fmt.Println(numString)
}

游乐场：https://play.golang.org/p/Hp1nac358HK

输出：

1.6666666666666667
1.6666666666666667

Float64 类型打印为 Golang 中的 int

Float64 type printing as int in Golang

floating-point

types

go

strconv