strconv.ParseInt给出0

Question

I'm trying to parse a file of this forme:

12
0,1,2,3,1,2,3,4,2,3,4,5
1,0,1,2,2,1,2,3,3,2,3,4
2,1,0,1,3,2,1,2,4,3,2,3
3,2,1,0,4,3,2,1,5,4,3,2
1,2,3,4,0,1,2,3,1,2,3,4
2,1,2,3,1,0,1,2,2,1,2,3
3,2,1,2,2,1,0,1,3,2,1,2
4,3,2,1,3,2,1,0,4,3,2,1
2,3,4,5,1,2,3,4,0,1,2,3
3,2,3,4,2,1,2,3,1,0,1,2
4,3,2,3,3,2,1,2,2,1,0,1
5,4,3,2,4,3,2,1,3,2,1,0
0,5,2,4,1,0,0,6,2,1,1,1
5,0,3,0,2,2,2,0,4,5,0,0
2,3,0,0,0,0,0,5,5,2,2,2
4,0,0,0,5,2,2,10,0,0,5,5
1,2,0,5,0,10,0,0,0,5,1,1
0,2,0,2,10,0,5,1,1,5,4,0
0,2,0,2,0,5,0,10,5,2,3,3
6,0,5,10,0,1,10,0,0,0,5,0
2,4,5,0,0,1,5,0,0,0,10,10
1,5,2,0,5,5,2,0,0,0,5,0
1,0,2,5,1,4,3,5,10,5,0,2
1,0,2,5,1,0,3,0,10,0,2,0

Where the first line give us the size of the matrix: n x n The n-following lines are the matrix D. Then the n-following lines are the matrix W. So there is 2n + 1 lines.

Here is the code to parse it and put it in variables.

func readFile(path string) (int64, Matrix, Matrix) {
    // open the file
    f, _ := os.Open(path)
    defer f.Close()

    // init the new reader on the opened file
    r := bufio.NewReader(f)

    // we get the n value
    line, _ := r.ReadString('
')
    splitedLine := strings.Fields(line)
    tmp, _ := strconv.ParseInt(splitedLine[0], 10, 64)
    n := int64(tmp)

    // we init the matrix W and D
    D := Matrix{}
    D.matrix = make([][]int64, n)
    for i, _ := range D.matrix {
        D.matrix[i] = make([]int64, n)
    }

    W := Matrix{}
    W.matrix = make([][]int64, n)
    for i, _ := range W.matrix {
        W.matrix[i] = make([]int64, n)
    }

    // loop on the n first element
    iter := int64(0)
    for iter < n {
        // we get the n following elements
        line, _ = r.ReadString('
')
        for index, ele := range strings.Split(line, ",") {
            D.matrix[iter][index], _ = strconv.ParseInt(ele, 10, 64)
        }
        iter++
    }

    iter = 0
    for iter < n {
        // we get the n following elements
        line, _ = r.ReadString('
')
        for index, ele := range strings.Split(line, ",") {
            W.matrix[iter][index], _ = strconv.ParseInt(ele, 10, 64)
        }
        iter++
    }

    return n, W, D

}

The resultat for W should be like:

[ 0.,  1.,  2.,  3.,  1.,  2.,  3.,  4.,  2.,  3.,  4.,  5.],
[ 1.,  0.,  1.,  2.,  2.,  1.,  2.,  3.,  3.,  2.,  3.,  4.],
[ 2.,  1.,  0.,  1.,  3.,  2.,  1.,  2.,  4.,  3.,  2.,  3.],
[ 3.,  2.,  1.,  0.,  4.,  3.,  2.,  1.,  5.,  4.,  3.,  2.],
[ 1.,  2.,  3.,  4.,  0.,  1.,  2.,  3.,  1.,  2.,  3.,  4.],
[ 2.,  1.,  2.,  3.,  1.,  0.,  1.,  2.,  2.,  1.,  2.,  3.],
[ 3.,  2.,  1.,  2.,  2.,  1.,  0.,  1.,  3.,  2.,  1.,  2.],
[ 4.,  3.,  2.,  1.,  3.,  2.,  1.,  0.,  4.,  3.,  2.,  1.],
[ 2.,  3.,  4.,  5.,  1.,  2.,  3.,  4.,  0.,  1.,  2.,  3.],
[ 3.,  2.,  3.,  4.,  2.,  1.,  2.,  3.,  1.,  0.,  1.,  2.],
[ 4.,  3.,  2.,  3.,  3.,  2.,  1.,  2.,  2.,  1.,  0.,  1.],
[ 5.,  4.,  3.,  2.,  4.,  3.,  2.,  1.,  3.,  2.,  1.,  0.]

But when I print it; it gives me :

[0 1 2 3 1 2 3 4 2 3 4 0]
[1 0 1 2 2 1 2 3 3 2 3 0]
[2 1 0 1 3 2 1 2 4 3 2 0]
[3 2 1 0 4 3 2 1 5 4 3 0]
[1 2 3 4 0 1 2 3 1 2 3 0]
[2 1 2 3 1 0 1 2 2 1 2 0]
[3 2 1 2 2 1 0 1 3 2 1 0]
[4 3 2 1 3 2 1 0 4 3 2 0]
[2 3 4 5 1 2 3 4 0 1 2 0]
[3 2 3 4 2 1 2 3 1 0 1 0]
[4 3 2 3 3 2 1 2 2 1 0 0]
[5 4 3 2 4 3 2 1 3 2 1 0]

I don't know why. Thanks for your reply.

Answer 1

Know that Reader.ReadString() returns you a string value with the delimieter. So r.ReadString(' ') will return you a string with the trailing newline character.

And when you split the string at the commas, the last part will contain the newline character, and attempting to parse the number from it will fail, as shown in this example:

line := "0,1,2
"
for _, ele := range strings.Split(line, ",") {
    fmt.Println(strconv.ParseInt(ele, 10, 64))
}

Output (try it on the Go Playground):

0 <nil>
1 <nil>
0 strconv.ParseInt: parsing "2
": invalid syntax

You religiously omit error checks, don't do that! As you can see in the above example, checking and printing the error returned by strconv.ParseInt() immediately revealed the error and what's going wrong.

What you may do is cut the trailing newline character before attempting to parse any number from it, e.g.:

strconv.ParseInt(strings.TrimSpace(ele), 10, 64)

Or use the bufio.Scanner which can scan lines and it cuts trailing newlines automatically.