Loops

For loops

for i in 1:20 {
  print(i) // Prints 1, 2, 3, ..., 20
}

for j in 1:2:20 { // You can increment/decrement by other values
  print(j) // Prints 1, 3, 5, ..., 19
}

For loops will always loop over an array:

• Ranges like 1:20 or 1:2:20 are arrays of numbers, and it loops over the values of that array.
• Structs are converted into an array of tuples of (member, value), and it loops over each of those tuples.
• Arrays, strings and maps are looped over by their indices, uint for arrays and strings and the key defined for maps.

While loops

mut int j = 2
while j > 0 {
  j--
}
// `j` is available here since it was declared outside

Labels, break, and continue

There are break and continue keywords for breaking out of the loop, and skipping to the next iteration, respectively.

However, if you have a label on your loop, you can put the label name after break or continue to break or continue from that label. This is very useful if you have nested loops, for instance.

int[][] table = [[...]]

rows: for row in table {
// ^ This is a label

  for col in table[row] {
    int val = table[row][col]

    match val {
      2 -> { continue } // This will skip to the next value in the inner loop
      3 -> { break } // This will break out of the inner loop
      5 -> { continue :rows } // This will skip to the next value in the outer loop
      10 -> { break :rows } // This will break out of the outer loop and go to the `print("Hello world")` below
      _ -> {}
    }

    print(val)
  }
}

print("Hello world")