# Concatenating two lists or a list and an element: concat augment

### 5.40.13 Concatenating two lists or a list and an element: concat augment

The concat command combines to lists or adds an element to a list.
augment is a synonym for concat.

- concat takes two arguments:
  L1 and L2, two lists or a list and an element (in any order).
- concat(L1,L2) returns a list consisting of the elements of L1 (or L1 itself if it isn’t a list) followed by the elements of L2 (or L2 itself).

#### Examples.

- Input:
  concat([3,4,2],[1,2,4])
  or:
  augment([3,4,2],[1,2,4])
  Output:

  ⎡ ⎣ | 3,4,2,1,2,4 | ⎤ ⎦

- Input:
  concat([3,4,2],5)
  or:
  augment([3,4,2],5)
  Output:

  ⎡ ⎣ | 3,4,2,5 | ⎤ ⎦

- Input:
  concat(2,[5,4,3])
  or:
  augment(2,[5,4,3])
  Output:

  ⎡ ⎣ | 2,5,4,3 | ⎤ ⎦

Warning.
Input:

concat([[3,4,2]],[[1,2,4]])

or:

augment([[3,4,2]],[[1,2,4]])

results in:
Output:

⎡
⎣

3 | 4 | 2 | 1 | 2 | 4

⎤
⎦