#### 17.3.20 concatenate [Function]

`concatenate` result-type &rest sequences ⇒ result-sequence

#### Arguments and Values::

result-type—a sequence type specifier.

sequences—a sequence.

result-sequence—a proper sequence of type result-type.

#### Description::

concatenate returns a sequence that contains all the individual elements of all the sequences in the order that they are supplied. The sequence is of type result-type, which must be a subtype of type sequence.

All of the sequences are copied from; the result does not share any structure with any of the sequences. Therefore, if only one sequence is provided and it is of type result-type, concatenate is required to copy sequence rather than simply returning it.

It is an error if any element of the sequences cannot be an element of the sequence result.

[Reviewer Note by Barmar: Should signal?]

If the result-type is a subtype of list, the result will be a list.

If the result-type is a subtype of vector, then if the implementation can determine the element type specified for the result-type, the element type of the resulting array is the result of upgrading that element type; or, if the implementation can determine that the element type is unspecified (or `*`), the element type of the resulting array is t; otherwise, an error is signaled.

#### Examples::

    (concatenate 'string "all" " " "together" " " "now") ⇒  "all together now"
    (concatenate 'list "ABC" '(d e f) #(1 2 3) #*1011)
    ⇒  (#\A #\B #\C D E F 1 2 3 1 0 1 1)
    (concatenate 'list) ⇒  NIL

      (concatenate '(vector * 2) "a" "bc") should signal an error

#### Exceptional Situations::

An error is signaled if the result-type is neither a recognizable subtype of list, nor a recognizable subtype of vector.

An error of type type-error should be signaled if result-type specifies the number of elements and the sum of sequences is different from that number.

#### See Also::

append