6.40.16  Rotating a list: rotate

The rotate command rotates a list; namely it moves elements from one side and puts them on the other.

• rotate takes one mandatory argument and one optional argument:
  • L, a list.
  • Optionally, n, an integer (by default n=−1).
• rotate(L) returns the list formed by rotating L n places to the left if n>0 or −n places to the right if n<0. Elements leaving the list from one side come back on the other side. By default n=−1 and the last element becomes the first.

Examples.

• Input:
  rotate([0,1,2,3,4])
  Output:

  ⎡ ⎣

  4,0,1,2,3

  ⎤ ⎦

• Input:
  rotate([0,1,2,3,4],2)
  Output:

  ⎡ ⎣

  2,3,4,0,1

  ⎤ ⎦

• Input:
  rotate([0,1,2,3,4],-2)
  Output:

  ⎡ ⎣

  3,4,0,1,2

  ⎤ ⎦