Specs

list() -- list() :: list()

List subtraction operator. Removes the first occurrence of an element on the left list for each element on the right.

Before Erlang/OTP 22, the complexity of a -- b was proportional to length(a) * length(b), meaning that it would be very slow if both a and b were long lists. In such cases, consider converting each list to a MapSet and using MapSet.difference/2.

As of Erlang/OTP 22, this operation is significantly faster even if both lists are very long, and using --/2 is usually faster and uses less memory than using the MapSet-based alternative mentioned above. See also the Erlang efficiency guide.

Inlined by the compiler.

Examples

iex> [1, 2, 3] -- [1, 2]
[3]

iex> [1, 2, 3, 2, 1] -- [1, 2, 2]
[3, 1]

The --/2 operator is right associative, meaning:

iex> [1, 2, 3] -- [2] -- [3]
[1, 3]

As it is equivalent to:

iex> [1, 2, 3] -- ([2] -- [3])
[1, 3]