i have problem with Lua goto. An error occurs after running the script : undefined label 'back'

Code:

function determinant()
det = 1
for k = n, 2, -1 do
    if a[k][k] == 0 then
        goto skok_jedna
    end
    ::back::
    for l = 1, k-1 do
        for m = 1, k-1 do
            a[l][m] = a[l][m] - a[l][k] * a[k][m] / a[k][k]
        end
    end
    det = det * a[k][k]
end
det = det * a[1][1]
goto konec_det

::skok_jedna::
l = k

::skok_dva::
l = l - 1
if l == 0 then
    det = 0
    return
end

if a[l][k] == 0 then 
    goto skok_dva
end

for m = 1, k do
    c[n] = a[l][m] 
    a[l][m] = a[k][m]
    a[k][m] = c[m]
end

det = det * -1
goto back 
::konec_det::
end

The script is part of a program to calculate a system of linear equations of n-variables using Cramer's rule.

Where is problem ? Thx all for reply

CodePudding user response：

The Lua manual says:

1. A label is visible in the entire block where it is defined, except inside nested functions.
2. A goto may jump to any visible label as long as it does not enter into the scope of a local variable.

What's going on in your code:

1. The label back is invisible from the line goto back
2. You're jumping inside the scope of loop variable k

CodePudding user response：

Thx for reply. I solve this problem with second function (remove goto from for-loop and goto back to for-loop):

function determinant()
det = 1
for k = n, 2, -1 do
    if a[k][k] == 0 then
        det2 {k}
        if det == 0 then
            return
        end
    end

    for l = 1, k-1 do
        for m = 1, k-1 do
            a[l][m] = a[l][m] - a[l][k] * a[k][m] / a[k][k]
        end
    end
    det = det * a[k][k]
end
det = det * a[1][1]
end

function det2(k)
l = k
::skok_dva::
l = l - 1
if l == 0 then
    det = 0
    return
end
if a[l][k] == 0 then 
    goto skok_dva
end
for m = 1, k do
    c[n] = a[l][m] 
    a[l][m] = a[k][m]
    a[k][m] = c[m]
end
det = det * -1
end