91 lines
3.1 KiB
Common Lisp
91 lines
3.1 KiB
Common Lisp
;5.
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;a) Write twice the n-th element of a linear list. Example: for (10 20 30 40 50) and n=3 will produce (10 20 30 30 40 50).
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;duplicate-nth-element(l1l2...ln, n) =
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; empty list if l1l2...ln is empty
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; l1 + l1l2...ln if n = 1
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; l1 + duplicate-nth-element(l2...ln, n) otherwise
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(defun duplicate-nth-element (lst n)
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(cond
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((null lst) nil)
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((< n 1 ) lst )
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((= n 1) (cons (car lst) lst))
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(t (cons (car lst) (duplicate-nth-element (cdr lst) (- n 1))))
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)
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)
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(print (duplicate-nth-element '(10 20 30 40 50) 3))
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(print (duplicate-nth-element '(10 20 30 40 50) 30))
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(print (duplicate-nth-element '(10 20 30 40 50) -1))
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;b) Write a function to return an association list with the two lists given as parameters.
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; Example: (A B C) (X Y Z) --> ((A.X) (B.Y) (C.Z)).
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;create-association-list(l1l2...ln, m1m2...mn) =
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; empty list if l1l2...ln and m1m2...mn are empty
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; (l1, m1) + create-association-list(l2...ln, m2...mn) otherwise
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; (l1, nil) + create-association-list(l2...ln, m1m2...mn) if m1m2...mn is empty
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; (nil, m1) + create-association-list(l1l2...ln, m2...mn) if l1l2...ln is empty
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(defun create-association-list (list1 list2)
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(if (and (null list1) (null list2))
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'()
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(let ((key (car list1))
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(value (car list2)))
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(cons (cons key value)
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(create-association-list (cdr list1) (cdr list2))))))
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(print (create-association-list '(A B C) '(X Y Z)))
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(print (create-association-list '(A B) '(X Y Z)))
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(print (create-association-list '(A B C) '(X Y)))
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;c) Write a function to determine the number of all sublists of a given list, on any level. A sublist is either the list itself, or any element that is a list, at any level. Example:
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;(1 2 (3 (4 5) (6 7)) 8 (9 10)) => 5 lists:
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;(list itself, (3 ...), (4 5), (6 7), (9 10)).
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;count-sublists-helper(l1l2...ln) =
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; 0 if l1l2...ln is empty
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; 1 + count-sublists-helper(l2...ln) + count-sublists-helper(l1) if l1 is a list
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; count-sublists-helper(l2...ln) otherwise
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(defun count-sublists-helper (lst)
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(if (null lst)
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0
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(let ((head (car lst))
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(tail (cdr lst)))
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(if (listp head)
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(+ 1 (count-sublists-helper head) (count-sublists-helper tail))
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(count-sublists-helper tail)))))
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;count-sublists(lst) =
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; 0 if lst is empty
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; 1 + count-sublists-helper(lst) otherwise
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(defun count-sublists (lst)
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(if (listp lst)
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(+ 1 (count-sublists-helper lst))
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0))
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(print (count-sublists '(1 2 (3 (4 5) (6 7)) 8 (9 10))))
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(print (count-sublists '(1 2 (3 (4 5) (6 7)) 8 (9 10) (11))))
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;d) Write a function to return the number of all numerical atoms in a list at superficial level.
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;count-numerical-atoms(l1l2...ln) =
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; 0 if l1l2...ln is empty
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; 1 + count-numerical-atoms(l2...ln) if l1 is a number
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; count-numerical-atoms(l2...ln) otherwise
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(defun count-numerical-atoms (lst)
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(if (null lst)
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0
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(let ((head (car lst))
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(tail (cdr lst)))
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(if (numberp head)
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(+ 1 (count-numerical-atoms tail))
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(count-numerical-atoms tail)))))
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(print(count-numerical-atoms '(1 2 (3 (4 5) (6 7)) 8 (9 10))))
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(exit)
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