Write a 3-argument function replace which takes a list ls, an integer n and an value x as arguments, and returns a list where the element in the n th position has been replaced by x. The other elements in the list should stay the same as before. The positions start with 0. If n is not a valid position in ls, then ls itself should be returned.This needs to be done in standard ML.
sample test cases:
– replace; val it = fn: ’a list * int * ’a -> ’a list –
replace(nil, 2, 3); val it = []: int list
– replace([1,2,4], 2, 3); val it = [1, 2, 3]: int list
– replace([1,2,4], 5, 0); val it = [1, 2, 4]: int list
– replace([2.3, 5.0, 2.001, 1.11], 1, 50.0); val it = [2.3, 50.0, 2.001, 1.11]: real list
