Map n-to-m: mapcan function (Personal website)

Map n-to-m: `mapcan` function

A higher-order Elisp function that maps n elements to m elements ¹⁸:

(mapcan (lambda (x)
          (pcase x
            (10 '(100))       ; map
            (20 '())          ; filter
            (30 '(300 300)))) ; flat-map
        '(10 20 30))

(100 300 300)

(mapcan #'identity '((10) (20) (30))) ; flatten

(10 20 30)

Gotcha with destructive concatenation

Footnotes

(18)

Accepts lists, vectors, and strings, and always returns a list.