lambda - Variadic append function (append any number of lists together) -


i'm trying implement scheme procedure append myself. simplest version append 2 lists quite easy , can done with:

 (define (append lis1 lis2)                   (if (null? lis1)                      lis2                     (cons (car lis1)                           (append (cdr lis1) lis2))))

the trouble starts when want append any number of lists. 0 lists , 1 lists the idea simple, im having real hard time thinking how apply procedure number of lists... appreciated, oren

Óscar's answer reverse input , use foldl instead foldl implemented proper tail call.

(define (append* . xs)   (foldl append null (reverse xs)))

output same

(append* '(1 2) '(3) '(4 5 6) '(7 8)) => '(1 2 3 4 5 6 7 8)

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