Extract a sub-list : mid

### 2.37.3 Extract a sub-list : `mid`

See also : `at` section 2.37.2.
`mid` is used to extract a sub-list of a list.
`mid` takes as argument a list, the index of the begining of the sub-list and the length of the sub-list.
`mid` returns the sub-list.
Input :

`mid([0,1,2,3,4,5],2,3)`

Output :

`[1,2,3]`

Warning
`mid` can not be used to extract a subsequence of a sequence, because the arguments of `mid` would be merged with the sequence. Index notation must be used, like e.g.`(0,1,2,3,4,5)[2..3]`.