#####   ######  #####    ###    #   #  ###  #   #  ######
##  ##  ##      ##  ##  ## ##   #   #   #   #   #  ##
#####   ####    #####   #   #   #   #   #   #   #  ####
##  #   ##      ##      ## ##    # #    #    # #   ##
##   #  ######  ##       ###      #    ###    #    ######

$ curl repovive.com/roadmaps/go/loops/off-by-one-errors

░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░███████████████████████████████████████████████████████

#####   ######  #####    ###    #   #  ###  #   #  ######
##  ##  ##      ##  ##  ## ##   #   #   #   #   #  ##
#####   ####    #####   #   #   #   #   #   #   #  ####
##  #   ##      ##      ## ##    # #    #    # #   ##
##   #  ######  ##       ###      #    ###    #    ######

$ curl repovive.com/roadmaps/go/loops/off-by-one-errors

Repovive

Off-By-One Errors - Loops | Go | Repovive

Repovive.

Go10 sections · 431 units20h total

Open in Course

Off-By-One Errors

Boundary mistakes

Off-by-one errors are common in loops:

nums := []int{1, 2, 3}
// Bug: should be i < len(nums)
for i := 0; i <= len(nums); i++ {
    fmt.Println(nums[i]) // Panics on last iteration
}

Use < for zero-based indices, not <=. A slice of length $3$ has valid indices $0$ , $1$ , $2$ . Index $3$ is out of bounds. When in doubt, trace through your loop by hand.