> x <- c("a", "a")
> diff_element(c(x, "a", "b", "c"), c(x, "a", "b"), width = 20)
    x   | y      
[2] "a" | "a" [2]
[3] "a" | "a" [3]
[4] "b" | "b" [4]
[5] "c" -        

> diff_element(c(x, "a", "b"), c(x, "a", "b", "c"), width = 20)
    x   | y      
[2] "a" | "a" [2]
[3] "a" | "a" [3]
[4] "b" | "b" [4]
        - "c" [5]

> diff_element(c(x, "a", "B", "c"), c(x, "a", "b", "c"), width = 20)
    x   | y      
[1] "a" | "a" [1]
[2] "a" | "a" [2]
[3] "a" | "a" [3]
[4] "B" - "b" [4]
[5] "c" | "c" [5]

> # context
> diff_element(c(letters, "a", "b"), c(letters, "a", "b", "c"), width = 20)
     x   | y       
[26] "z" | "z" [26]
[27] "a" | "a" [27]
[28] "b" | "b" [28]
         - "c" [29]

