Elisp: Sequence. Join, Convert

By Xah Lee. Date: . Last updated: .

Convert to Vector, Join Vectors

vconcat

(vconcat sequence1 sequence2 etc)

If a sequence is a string, each character is converted into a integer of its Code Point

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

;; join vector and list
(vconcat (vector 3 4) (list "a" "b"))
;; [3 4 "a" "b"]
;; If a sequence is a string, each character is converted into a integer of its Codepoint

(vconcat "abc")
;; [97 98 99]

Convert to List, Join Lists

append

(append sequence1 sequence2 etc)

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

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

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

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

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

;; join vectors and lists to list
(append (vector 1 2 3) (vector 4 5) (list 6))
;; (1 2 3 4 5 6)
;; proper list
;; If a sequence is a string, each character is converted into a integer of its Codepoint

(append "abc" nil)
;; (97 98 99)

Sequence to String

Join Sequences, to List or Vector

seq-concatenate

(seq-concatenate TYPE SEQUENCE...)

join sequences, into a list or vector.

(this is a generalized version of vconcat and append)

;; 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 considered as char id
;; 97 is char a

Convert a Sequence to List or Vector

seq-into

(seq-into SEQUENCE TYPE)

convert sequence to a specific TYPE.

TYPE is one of: 'vector 'list 'string

(this is a generalized version of vconcat and append)

(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])