fold

fold

Generic left-fold procedure. It is defined for multiple lists, multiple vectors, and single tables and sets.

(fold (lambda (x acc) (* x acc)) 1 '(2 3 5)) ; 30

(let ()
   (def multiplexer
      (lambda (x y z acc) (pair (list x y z) acc))) 
   (fold multiplexer () '(1 2 3) '(a b c) '(foo bar baz)))

; ((3 c baz) (2 b bar) (1 a foo))

(fold (lambda (x acc) (* x acc)) 1 #(vector 2 3 5)) ; 30

(fold (lambda (x acc) (pair x.head (* x.tail acc.tail)))
      (0 . 1)
      #(vector 2 3 5)
      index: true)

; (2 . 30)

(fold (lambda (x y z acc) (* x y z acc))
      10
      (vector 1 2 3)
      (vector 4 5 6)
      (vector 7 8 9))

; 3628800

(let (t (: foo 2 bar 3))
   (proc combiner (x acc)
      (acc.add x.head x.tail))
   (fold combiner (set) t))

; (set foo 2 3 bar)

(let (s (set 2 3 5))
   (fold * 1 s))

; 30