How to use fmt.Sscan to parse integers into an array?

huangapple
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英文:

How to use fmt.Sscan to parse integers into an array?

问题

我正在尝试将一个字符串中的整数列表扫描到一个数组（或者可以选择使用切片）中。

  1. package main
  3. import "fmt"
  5. func main() {
  6.     var nums [5]int
  7.     n, _ := fmt.Sscan("1 2 3 4 5", &nums)  // 这样不起作用
  8.     fmt.Println(nums)
  9. }

为了使这段代码起作用，你需要将什么作为Sscan的第二个参数传递？

我知道可以传递nums[0]，nums[1]...等等，但我更希望只传递一个参数。

英文:

I'm trying to scan a list of integers from a string into an array (or alternatively, a slice)

  1. package main
  3. import "fmt"
  5. func main() {
  6. 	var nums [5]int
  7.     n, _ := fmt.Sscan("1 2 3 4 5", &nums)  // doesn't work
  8.     fmt.Println(nums)
  9. }

What do I need to pass as second argument to Sscan in order for this to work?

I know I could pass nums[0], nums[1] ... etc., but I'd prefer a single argument.

答案1

得分: 6

我不认为这可以作为一个方便的一行代码来实现。因为Sscan接受...interface{}参数，所以你需要传递一个接口切片，因此需要先将你的数组转换为接口切片：

  1. func main() {
  2.     var nums [5]int
  4.     // 转换为接口切片
  5.     xnums := make([]interface{}, len(nums))
  6.     for n := range nums {
  7.         xnums[n] = &nums[n]
  8.     }
  10.     n, err := fmt.Sscan("1 2 3 4 5", xnums...)
  11.     if err != nil {
  12.         fmt.Printf("field %d: %s\n", n+1, err)
  13.     }
  15.     fmt.Println(nums)
  16. }

显然，你可以在接口切片中混合不同类型的值，这样可以更容易地扫描更复杂的字符串。对于仅包含以空格分隔的整数，你可能更好地使用strings.Split或bufio.Scanner以及strconv.Atoi。

英文:

I don't think this is possible as a convenient one-liner. As Sscan takes ...interface{}, you would need to pass slice of interfaces as well, hence converting your array first:

  1. func main() {
  2. 	var nums [5]int
  4. 	// Convert to interfaces
  5. 	xnums := make([]interface{}, len(nums))
  6. 	for n := range nums {
  7. 		xnums[n] = &nums[n]
  8. 	}
  10. 	n, err := fmt.Sscan("1 2 3 4 5", xnums...)
  11. 	if err != nil {
  12. 		fmt.Printf("field %d: %s\n", n+1, err)
  13. 	}
  15. 	fmt.Println(nums)
  16. }

http://play.golang.org/p/1X28J7JJwl

Obviously you could mix different types in your interface array, so it would make the scanning of more complex string easier. For simply space-limited integers, you might be better using strings.Split or bufio.Scanner along with strconv.Atoi.

答案2

得分: 3

为了使其适用于不仅仅是硬编码的字符串，最好使用bufio.Scanner和io.Reader接口来完成这个任务：

  1. package main
  3. import (
  4. 	"bufio"
  5. 	"fmt"
  6. 	"io"
  7. 	"strconv"
  8. 	"strings"
  9. )
  11. func scanInts(r io.Reader) ([]int, error) {
  12. 	s := bufio.NewScanner(r)
  13. 	s.Split(bufio.ScanWords)
  14. 	var ints []int
  15. 	for s.Scan() {
  16. 		i, err := strconv.Atoi(s.Text())
  17. 		if err != nil {
  18. 			return ints, err
  19. 		}
  20. 		ints = append(ints, i)
  21. 	}
  22. 	return ints, s.Err()
  23. }
  25. func main() {
  26. 	input := "1 2 3 4 5"
  27. 	ints, err := scanInts(strings.NewReader(input))
  28. 	if err != nil {
  29. 		fmt.Println(err)
  30. 	}
  31. 	fmt.Println(ints)
  32. }

输出结果：

[1 2 3 4 5]

Playground

英文:

To allow this to work on more than just hard-coded strings, it's probably better to use a bufio.Scanner, and an io.Reader interface to do this:

  1. package main
  3. import (
  4. 	"bufio"
  5. 	"fmt"
  6. 	"io"
  7. 	"strconv"
  8. 	"strings"
  9. )
  11. func scanInts(r io.Reader) ([]int, error) {
  12. 	s := bufio.NewScanner(r)
  13. 	s.Split(bufio.ScanWords)
  14. 	var ints []int
  15. 	for s.Scan() {
  16. 		i, err := strconv.Atoi(s.Text())
  17. 		if err != nil {
  18. 			return ints, err
  19. 		}
  20. 		ints = append(ints, i)
  21. 	}
  22. 	return ints, s.Err()
  23. }
  25. func main() {
  26. 	input := "1 2 3 4 5"
  27. 	ints, err := scanInts(strings.NewReader(input))
  28. 	if err != nil {
  29. 		fmt.Println(err)
  30. 	}
  31. 	fmt.Println(ints)
  32. }

Produces:

>[1 2 3 4 5]

Playground

答案3

得分: 1

除非你特别想使用Sscann，否则你也可以尝试以下替代方法：

  • 将输入字符串按空格分割
  • 遍历结果数组
  • 将每个字符串转换为整数
  • 将结果值存储到整数切片中

像这样：

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"strconv"
  6. 	"strings"
  7. )
  9. func main() {
  11. 	nums := make([]int, 0)
  12. 	for _, s := range strings.Split("1 2 3 4 5", " ") {
  13. 		i, e := strconv.Atoi(s)
  14. 		if e != nil {
  15. 			i = 0 // 如果不是数字，默认为0
  16. 		}
  17. 		nums = append(nums, i)
  18. 	}
  19. 	fmt.Println(nums)
  20. }

http://play.golang.org/p/rCZl46Ixd4

英文:

Unless you're trying to use Sscann specifically you can also try this as an alternative:

  • split the input string by spaces
  • iterate the resulting array
  • convert each string into an int
  • store the resulting value into an int slice

Like this:

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"strconv"
  6. 	"strings"
  7. )
  9. func main() {
  11. 	nums := make([]int, 0)
  12. 	for _, s := range strings.Split("1 2 3 4 5", " ") {
  13. 		i, e := strconv.Atoi(s)
  14. 		if e != nil {
  15. 			i = 0 // that was not a number, default to 0
  16. 		}
  17. 		nums = append(nums, i)
  18. 	}
  19. 	fmt.Println(nums)
  20. }

http://play.golang.org/p/rCZl46Ixd4

huangapple
  • 本文由 发表于 2015年2月19日 18:58:32
  • 转载请务必保留本文链接：https://go.coder-hub.com/28604563.html
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