- Expr1 ++ Expr2
- Expr1 -- Expr2
The list concatenation operator ++ appends its second argument to its first and returns the resulting list.
The list subtraction operator — produces a list that is a copy of the first argument. The procedure is a follows: for each element in the second argument, the first occurrence of this element (if any) is removed.
- 1> [1,2,3]++[4,5].
- 2> [1,2,3,2,1,2]--[2,1,2].
The complexity of A — B is proportional to length(A)*length(B). That is, it becomes very slow if both A and B are long lists.