我正在阅读Caleb Doxsey的Go书,我有两个关于fmt.Scanf
http://www.golang-book.com/4的问题
我想知道为什么程序在第二个Scanf之后没有停止并等待用户输入?如何测试用户是否输入了整数和/或没有留空?
package main
import (
"fmt"
//"math"
)
// compute square roots by using Newton's method
func main() {
var x float64 //number to take square root
var y float64 //this is the guess
var q float64 //this is the quotient
var a float64 //this is the average
// how do check if the user entered a number
fmt.Print("Enter a number to take its square root: ")
var inputSquare float64
fmt.Scanf("%f", &inputSquare)
// why doesn't program stop after
// the Print statement and wait
// for user input?
fmt.Print("Enter first guess ")
var inputGuess float64
fmt.Scanf("%f", &inputGuess)
//x = 2
x = inputSquare
y = inputGuess
for i := 0; i < 10; i++ { //set up the for loop for iterations
q = x/y //compute the quotient; x and y are given
a = (q + y) / x //compute the average
y = a //set the guess to the average
} //for the next loop
fmt.Println("y --> ", y)
//fmt.Println("Sqrt(2)", math.Sqrt(2))
}
答案 0 :(得分:10)
它是Issue 5391:fmt
:Scanf
在Windows的行尾拒绝\r\n
。
作为一种解决方法并检查有效输入,请写
var inputSquare float64
n, err := fmt.Scanf("%f\n", &inputSquare)
if err != nil || n != 1 {
// handle invalid input
fmt.Println(n, err)
}
和
var inputGuess float64
n, err = fmt.Scanf("%f\n", &inputGuess)
if err != nil || n != 1 {
// handle invalid input
fmt.Println(n, err)
}
变通方法是"%f\n"
格式字符串中的换行符。
套餐
fmt
func Scanf(format string, a ...interface{}) (n int, err error)
Scanf
扫描从标准输入读取的文本,并连续存储 由空格分隔的值到连续的参数中 格式。它返回成功扫描的项目数。
这是一个完整的工作计划:
package main
import (
"fmt"
)
// compute square roots by using Newton's method
func main() {
var x float64 //number to take square root
var y float64 //this is the guess
var q float64 //this is the quotient
var a float64 //this is the average
fmt.Print("Enter a number to take its square root: ")
var inputSquare float64
n, err := fmt.Scanf("%f\n", &inputSquare)
if err != nil || n != 1 {
// handle invalid input
fmt.Println(n, err)
return
}
fmt.Print("Enter first guess ")
var inputGuess float64
n, err = fmt.Scanf("%f\n", &inputGuess)
if err != nil || n != 1 {
// handle invalid input
fmt.Println(n, err)
return
}
x = inputSquare
y = inputGuess
for i := 0; i < 10; i++ {
q = x / y // compute the quotient; x and y are given
a = (q + y) / x // compute the average
y = a // set the guess to the average
}
fmt.Printf("sqrt(%g) = %g\n", x, y)
}
输出:
Enter a number to take its square root: 2.0
Enter first guess 1.0
sqrt(2) = 1.414213562373095
我在Windows 7上使用Go 1.1.1:
C:\>go version
go version go1.1.1 windows/amd64