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1 EEL 5840 – Class #11 – Fall 2008^ University of Florida © Dr. A. Antonio Arroyo
EEL5840: Elements of Machine Intelligence
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2 EEL 5840 – Class #11 – Fall 2008^ University of Florida © Dr. A. Antonio Arroyo
EEL5840: Elements of Machine Intelligence
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• LISP LAB 3
> Examples & Selected Homework 3 Solutions > Optional Parameters in LISP > Other Types of Parameters in LISP > Functional Arguments
3 EEL 5840 – Class #11 – Fall 2008^ University of Florida © Dr. A. Antonio Arroyo
EEL5840: Elements of Machine Intelligence
Rous LISP Lab 2 - Examples
Are two SEXes equal? (defun EQAL (Sex1 Sex2) (cond ((ATOM Sex1) (EQ Sex1 Sex2)) ((ATOM Sex2) nil) ((EQAL (Car Sex1) (Car Sex2)) (EQAL (Cdr Sex1) (Cdr Sex2))) ))
4 EEL 5840 – Class #11 – Fall 2008^ University of Florida © Dr. A. Antonio Arroyo
EEL5840: Elements of Machine Intelligence
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What is the depth of a list? (defun Depth (Lis) (Cond ((Null Lis) 0) ((Atom Lis) 0) ( t (max (+ (Depth (Car Lis)) 1) (Depth (Cdr Lis)) )) ))
5 EEL 5840 – Class #11 – Fall 2008^ University of Florida © Dr. A. Antonio Arroyo
EEL5840: Elements of Machine Intelligence
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Unnest (defun unnest (lis) (cond ((null lis) lis) ( (atom (car lis)) (cons (car lis) (unnest (cdr lis)))) ( t (append (unnest (car lis)) (unnest (cdr lis))))))
-or- (defun unnest (lis) (cond ((null lis) nil) ((atom lis) (list lis)) (t (append (unnest (car lis)) (unnest (cdr lis)) ))) ))
6 EEL 5840 – Class #11 – Fall 2008^ University of Florida © Dr. A. Antonio Arroyo
EEL5840: Elements of Machine Intelligence
Rous (^) Hwk 3 - Selected Solutions
Setdiff (defun setdiff(s1 s2)(cond ((null s1) nil) ((member (car s1) s2) (setdiff (cdr s1) s2)) (t (cons (car s1) (setdiff (cdr s1) s2))) ))
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EEL5840: Elements of Machine Intelligence
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EQSet (defun eqset(s1 s2) (equal (setdiff s1 s2) (setdiff s2 s1)))
Makeset (defun makeset(lis)(cond ((null lis) nil) ((member (car lis) (cdr lis)) (makeset (cdr lis))) ( t (cons (car lis) (makeset (cdr lis)))) ))
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EEL5840: Elements of Machine Intelligence
Rous LISP Lab 3
- Optional Parameters in LISP We can elegantly define procedures that include optional para- meters in LISP by using the &OPTIONAL keyword in the argu- ment list of a function definition. By enclosing the parameter(s) that follow the &optional keyword in parentheses one can supply a default value (otherwise they are automatically defaulted to nil). More than one parameter can follow the &optional keyword.
- template : (defun fname (arg1 arg2 &optional arg3-argn) () )
- Example: Write a function to count the top-level elements of a list (defun count-top (lis &optional (answer 0)) (if (endp lis) answer (count-top (cdr lis) (+ 1 answer)) ))
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> (defun union2 (S1 S2 &optional (Ans)) (cond ( (null S1) (append Ans S2)) ( (member (car s1) S2) (union2 (cdr S1) S2 Ans)) ( 'else (union2 (cdr s1) S2 (append Ans (list (car S1))))) )) UNION > (union2 '(a b) '(c d)) (A B C D) > (union2 '(a) '(a b c d)) (A B C D) > (union2 '(a b) '(b c a)) (B C A)
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EEL5840: Elements of Machine Intelligence
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- Other Types of Parameters in LISP The &REST parameter in LISP is bound to a list of all otherwise accounted for argument values. Using this we could define a multiple list append as follows: > (defun manyappend (&rest lists)(app-h lists)) MANYAPPEND > (defun app-h (lists) (if (endp lists) nil (append (car lists) (app-h (cdr lists))) )) APP-H > (manyappend nil) NIL > (manyappend nil '(a b)) (A B) > (manyappend '(a b) '(c d) '(d e)) (A B C D D E) > (manyappend '(a b) nil '(c d)) (A B C D)
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- Keyword parameters are designated by &KEY to allow for the easy identification of many parameters and to bypass positional binding. Using this we can write two versions of member, one using EQ the other using EQUAL. (defun MYMEMBER (SEX LIS &KEY TESTFCN) (COND ((NULL LIS) NIL ) ((IF (NULL TESTFCN) (EQ SEX (CAR LIS)) (TESTFCN SEX (CAR LIS))) LIS ) ( T (MYMEMBER SEX (CDR LIS) :TESTFCN TESTFCN)) )) > (mymember 'a '(a b)) (A B) > (mymember '(a) '((a) (b)) :testfcn 'equal) Error: The function TESTFCN is not defined. Happened in: # 16 EEL 5840 – Class #11 – Fall 2008^ University of Florida © Dr. A. Antonio Arroyo
EEL5840: Elements of Machine Intelligence
Rous LISP Lab 3
- Using funcall we can fix MYMEMBER as follows: (defun mymember (sex lis &key testfcn) (cond ((null lis) nil ) ((if (null testfcn) (eq sex (car lis)) (funcall testfcn sex (car lis))) lis ) ( t (mymember sex (cdr lis) :testfcn testfcn)) ))
> (mymember '(a) '((a) (b))) NIL > (mymember '(a) '((a) (b)) :testfcn 'equal) ((A) (B)) > (mymember '(a) '((a) (b)) :testfcn 'eq) NIL
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