addition of a standard library

lib/stdlib.scm

@@ -0,0 +1,43 @@
+(define (not x)            (if x #f #t))
+(define (null? obj)        (if (eqv? obj '()) #t #f))
+(define (list . objs)       objs)
+(define (id obj)           obj)
+(define (flip func)        (lambda (arg1 arg2) (func arg2 arg1)))
+(define (curry func arg1)  (lambda (arg) (apply func (cons arg1 (list arg)))))
+(define (compose f g)      (lambda (arg) (f (apply g arg))))
+(define zero?              (curry = 0))
+(define positive?          (curry < 0))
+(define negative?          (curry > 0))
+(define (odd? num)         (= (mod num 2) 1))
+(define (even? num)        (= (mod num 2) 0))
+(define (foldr func end lst)
+  (if (null? lst)
+      end
+      (func (car lst) (foldr func end (cdr lst)))))
+(define (foldl func accum lst)
+  (if (null? lst)
+      accum
+      (foldl func (func accum (car lst)) (cdr lst))))
+(define fold foldl)
+(define reduce foldr)
+(define (unfold func init pred)
+  (if (pred init)
+      (cons init '())
+      (cons init (unfold func (func init) pred))))
+(define (sum . lst)         (fold + 0 lst))
+(define (product . lst)     (fold * 1 lst))
+(define (and . lst)         (fold && #t lst))
+(define (or . lst)          (fold || #f lst))
+(define (max first . rest) (fold (lambda (old new) (if (> old new) old new)) first rest))
+(define (min first . rest) (fold (lambda (old new) (if (< old new) old new)) first rest))
+(define (length lst)        (fold (lambda (x y) (+ x 1)) 0 lst))
+(define (reverse lst)       (fold (flip cons) '() lst))
+(define (mem-helper pred op) (lambda (acc next) (if (and (not acc) (pred (op next))) next acc)))
+(define (memq obj lst)       (fold (mem-helper (curry eq? obj) id) #f lst))
+(define (memv obj lst)       (fold (mem-helper (curry eqv? obj) id) #f lst))
+(define (member obj lst)     (fold (mem-helper (curry equal? obj) id) #f lst))
+(define (assq obj alist)     (fold (mem-helper (curry eq? obj) car) #f alist))
+(define (assv obj alist)     (fold (mem-helper (curry eqv? obj) car) #f alist))
+(define (assoc obj alist)    (fold (mem-helper (curry equal? obj) car) #f alist))
+(define (map func lst)      (foldr (lambda (x y) (cons (func x) y)) '() lst))
+(define (filter pred lst)   (foldr (lambda (x y) (if (pred x) (cons x y) y)) '() lst))