basics.scm

; this can be evaluated at https://inst.eecs.berkeley.edu/~cs61a/fa14/assets/interpreter/scheme.html

(define
 (square x)
 (* x x)
)

(define
 (range start length)
 (if
  (= start length)
  '()
  (cons start (range (+ start 1) length))
 )
)

(define
 (map f xs)
 (if
  (null? xs)
  xs
  (cons
   (f (car xs))
   (map f (cdr xs))
  )
 )
)

(define
 (sum xs)
 (if
  (null? xs)
  0
  (+ (car xs) (sum (cdr xs)))
 )
)


(define
 (fiboid a b reps)
 (if
  (< reps 1)
  '()
  (cons b (fiboid b (+ a b) (- reps 1)))
 )
)

(define (fib n) (fiboid 0 1 n))

(define
 (reduce fn xs init)
 (if
  (null? xs)
  init
  (reduce fn (cdr xs) (fn init (car xs)))
 )
)

(define
 (all xs)
 (cond
  ((null? xs) #t)
  ((not (car xs)) #f)
  (else (all (cdr xs)))
 )
)

(define
 (any xs)
 (cond
  ((null? xs) #f)
  ((car xs) #t)
  (else (any (cdr xs)))
 )
)

(define
 (filter fn xs)
 (cond
  ((null? xs) '())
  ((fn (car xs)) (cons (car xs) (filter fn (cdr xs))))
  (else (filter fn (cdr xs)))
 )
)

(define
 (reduce fn xs init)
 (if
  (null? xs)
  init
  (reduce fn (cdr xs) (fn init (car xs)))
 )
)

(define
 (squeeze fn)
 (lambda (xs) (apply fn xs))
)

(define
 (spread fn)
 (lambda (. args) (fn args))
)

(define
 (rev- old new)
 (if
  (null? old)
  new
  (rev- (cdr old) (cons (car old) new))
 )
)

(define (rev xs) (rev- xs '()))

(define
 (compose f g)
 (lambda (. args) (f (apply g args)))
)