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stdlib.scm
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stdlib.scm
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(define map
(let ((null? null?)
(car car)
(cdr cdr)
(cons cons)
(apply apply))
(letrec ((map-loop (lambda (f l . ls)
(if (null? l)
'() ; simplifying assumption: if l is empty, then ls is also empty
(if (null? ls)
(cons (f (car l)) (map-loop f (cdr l)))
(cons (apply f (car l) (map-loop car ls))
(apply map f (cdr l) (map-loop cdr ls))))))))
map-loop)))
(define fold-left
(let ((car car)
(cdr cdr)
(null? null?))
(lambda (f z xs)
(if (null? xs)
z
(fold-left f (f z (car xs)) (cdr xs))))))
(define fold-right
(let ((car car)
(cdr cdr)
(null? null?))
(lambda (f z xs)
(if (null? xs)
z
(f (car xs) (fold-right f z (cdr xs)))))))
(define append
(let ((null? null?)
(fold-right fold-right)
(cons cons))
(lambda args
(fold-right (lambda (e a)
(if (null? a)
e
(fold-right cons a e)))
'()
args))))
(define last-element
(let ((null? null?)
(cdr cdr)
(car car))
(lambda (l)
(if (null? (cdr l))
(car l)
(last-element (cdr l))))))
(define init
(let ((null? null?)
(cons cons)
(car car)
(cdr cdr))
(lambda (l)
(if (null? (cdr l))
'()
(cons (car l) (init (cdr l)))))))
(define cons*
(let ((null? null?)
(car car)
(cdr cdr)
(cons cons))
(letrec ((consrec* (lambda (z xs)
(if (null? (cdr xs))
(car xs)
(cons (car xs) (consrec* z (cdr xs)))))))
(lambda xs
(consrec* '() xs)))))
(define list
(lambda x
x))
(define list?
(let ((null? null?)
(pair? pair?)
(cdr cdr))
(letrec ((list?-loop (lambda (x)
(or (null? x)
(and (pair? x)
(list? (cdr x)))))))
list?-loop)))
(define length
(let ((fold-left fold-left)
(+ +))
(lambda (l)
(fold-left (lambda (acc e)
(+ acc 1))
0
l))))
(define make-string
(let ((null? null?)
(car car)
(make-string make-string))
(lambda (x . y)
(if (null? y)
(make-string x #\nul)
(make-string x (car y))))))
(define not
(lambda (x)
(if x
#f
#t)))
(define number?
(let ((float? float?)
(integer? integer?))
(lambda (x)
(or (float? x) (integer? x)))))
(define +
(let ((fold-left fold-left)
(+ +))
(lambda x
(fold-left + 0 x))))
(define *
(let ((fold-left fold-left)
(* *))
(lambda x
(fold-left * 1 x))))
(define -
(let ((apply apply)
(- -)
(+ +)
(null? null?))
(lambda (x . y)
(if (null? y)
(- 0 x)
(- x (apply + y))))))
(define /
(let ((apply apply)
(/ /)
(* *)
(null? null?))
(lambda (x . y)
(if (null? y)
(/ 1 x)
(/ x (apply * y))))))
(define =
(let ((= =)
(null? null?)
(car car)
(cdr cdr)
(apply apply))
(letrec ((=-loop (lambda (x . y)
(if (null? y)
#t ; simplifying assumption: x is a number
(and (= x (car y)) (apply =-loop x (cdr y)))))))
=-loop)))
(define <
(let ((null? null?)
(< <)
(car car)
(cdr cdr))
(letrec ((<-loop (lambda (element lst)
(if (null? lst)
#t
(and (< element (car lst))
(<-loop (car lst) (cdr lst)))))))
(lambda (x . y)
(<-loop x y)))))
(define >
(let ((null? null?)
(< <)
(= =)
(not not)
(car car)
(cdr cdr))
(letrec ((>-loop (lambda (element lst)
(if (null? lst)
#t
(and (not (or (< element (car lst))
(= element (car lst))))
(>-loop (car lst) (cdr lst)))))))
(lambda (x . y)
(>-loop x y)))))
(define zero?
(let ((= =))
(lambda (x)
(= x 0))))
(define string->list
(let ((string-ref string-ref)
(string-length string-length)
(< <)
(- -))
(lambda (s)
(letrec ((s->l-loop (lambda (n a)
(if (< n 0)
a
(s->l-loop (- n 1) (cons (string-ref s n) a))))))
(s->l-loop (- (string-length s) 1) '())))))
(define equal?
(let ((= =)
(string->list string->list)
(integer? integer?)
(float? float?)
(pair? pair?)
(char? char?)
(string? string?)
(eq? eq?)
(car car)
(cdr cdr)
(char->integer char->integer))
(letrec ((equal?-loop (lambda (x y)
(or (and (integer? x)
(integer? y)
(= x y))
(and (float? x)
(float? y)
(= x y))
(and (pair? x)
(pair? y)
(equal?-loop (car x) (car y))
(equal?-loop (cdr x) (cdr y)))
(and (char? x)
(char? y)
(= (char->integer x) (char->integer y)))
(and (string? x)
(string? y)
(equal?-loop (string->list x) (string->list y)))
(eq? x y)))))
equal?-loop)))