Elisp: Join or Convert List, Vector

Join Sequences to Vector

vconcat

(vconcat sequence1 sequence2 etc)

Join any Sequence Type and return a vector.

;; join vectors
(vconcat [3 4] ["a" "b"])
;; [3 4 "a" "b"]

;; join vector and list
(vconcat [3 4] '("a" "b"))
;; [3 4 "a" "b"]

;; join vector and string
(vconcat [3 4] "ab")
;; [3 4 97 98]

;; string elements are converted to char.
;; 97 is the codepoint for the char a

Join Sequences to List

append

(append sequence1 sequence2 etc)

Join any Sequence Type and return a list.

🛑 WARNING: if you want result to be Proper List , the last element must be a list, or nil.

join lists:

;; join lists
(append (list 1 2) (list 3 4))
;; (1 2 3 4)

convert vector to list:

;; convert vector to list
(append [1 2 3] nil)
;; (1 2 3)

;; this creates improper list
(append [1 2 3] [4 5])
;; (1 2 3 . [4 5])

;; this creates proper list
(append [1 2 3] [4 5] nil)
;; (1 2 3 4 5)

;; join vectors and lists to list
(append [1 2 3] [4 5] '(6))
;; (1 2 3 4 5 6)
;; proper list

Sequence to String

To convert a sequence to string, use mapconcat or format. [see Elisp: Format String]

mapconcat

(mapconcat function sequence separator)

Apply function to each element, and concat the results as string, with separator between elements.

;; list of numbers to string
(mapconcat 'number-to-string '(1 2 3) ",")
;; "1,2,3"

;; list to string
(mapconcat 'identity '("a" "b" "c") ",")
;; "a,b,c"

;; vector to string
(mapconcat 'number-to-string [1 2 3] ",")
;; "1,2,3"

Join Sequences, to List or Vector

seq-concatenate

(seq-concatenate TYPE SEQUENCE...)

join sequences, into a list or vector.

;; to list
(seq-concatenate 'list (list 1 2 3) (vector 4 5 6))
;; (1 2 3 4 5 6)

;; to vector
(seq-concatenate 'vector (list 1 2 3) (vector 4 5 6))
;; [1 2 3 4 5 6]

;; to string
(seq-concatenate 'string (list 97 98) (vector 99 100))
;; "abcd"
;; integer is consider a char id
;; 97 is char a

Convert single sequence to list or vector

seq-into

(seq-into SEQUENCE TYPE)

convert sequence to a specific TYPE.

TYPE is one of: 'vector 'list 'string

(seq-into (list 3 4) 'vector)
;; [3 4]

(seq-into (vector 3 4) 'list)
;; (3 4)

(seq-into "abc" 'list)
;; (97 98 99)
;; string elements are converted to char.
;; 97 is the codepoint for the char a

(seq-into "abc" 'vector)
;; [97 98 99]

(seq-into (vector 97 98 99) 'string)
;; "abc"

;; nested item is not converted

(seq-into (list 3 4 (list 3 4)) 'vector)
;; [3 4 (3 4)]

(seq-into (vector 3 4 (vector 5 6)) 'list)
;; (3 4 [5 6])