Exploring Array Manipulations and Functions in Common Lisp
This document from Montana State University, Summer 2003, delves into the intricacies of array declarations, element manipulations, and basic file I/O operations in Common Lisp. It discusses creating multi-dimensional arrays, accessing and modifying their contents, generating random numbers, formatted outputs, and includes exercises such as writing functions to find the smallest integer in an array and generating all permutations of a list. Ideal for those learning programming in Lisp and enhancing their understanding of data structures.
Exploring Array Manipulations and Functions in Common Lisp
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Presentation Transcript
Common Lisp! John Paxton Montana State University Summer 2003
Montana Facts • The Plains Indians began using buffalo jumps over 2000 years ago.
Array Declarations > (setf numbers (make-array '(4))) #(NIL NIL NIL NIL) > (setf numbers (make-array '(4) :initial-element 0)) #(0 0 0 0)
Array Declarations > (setf numbers (make-array '(4) :initial-contents '(1 2 3 4))) #(1 2 3 4) > (setf numbers (make-array '(2 3))) #2A((NIL NIL NIL) (NIL NIL NIL))
Array Access > (setf (aref numbers 0 0) 3) 3 > (setf (aref numbers 2 0) 3) *** - SYSTEM::STORE: subscripts (2 0) for #2A((3 NIL NIL) (NIL NIL NIL)) are out of range
Array Size Determination > (array-dimensions numbers) (2 3) > (array-dimension numbers 0) 2 > (array-dimension numbers 1) 3
Random Numbers > (random 10) ;; 0 – 9, integer 3 > (random 10.0) ;; [0.0, 10.0], real 4.7472386
Formatted Output > (format t “pronto") pronto > (format t "Senor ~% Lopez") Senor Lopez
Formatted Output > (format t "~a + ~a" 1 2) 1 + 2
Questions • Write a function that receives a 1-D integer array of size 5 and returns the value of the smallest integer contained in the array. • Declare a 3 by 5 matrix named numbers that initially contains all 7s.
Questions • Write a function called print-matrix that prints out the contents of the matrix that is passed in. Use the format statement. • Write a function called fill-matrix that gives each slot within the passed in matrix a random integer value between 0 and 10 inclusive.
File I/O (defun read-file ( file-name ) (with-open-file (data-file file-name :direction :input) (do ((item (read data-file nil) (read data-file nil))) ((not item) 'done) (format t "~a ~%" item) )))
File I/O • sample.dat file contents 1 2 3 4
File I/O > (read-file "sample.dat") 1 2 3 4 DONE
Question • Write a function that finds and prints all permutations of a list. For example, (permute ‘(1 2 3)) could print 1 2 3, 1 3 2, 2 1 3, 2 3 1, 3 1 2, 3 2 1
permute (defun permute (alist &optional (so-far nil)) (cond ((null alist) (format t "~a~%" so-far)) (t (dolist (item alist) (permute (remove item alist) (cons item so-far)) ))))
permute > (permute '(1 2 3)) (3 2 1) (2 3 1) (3 1 2) (1 3 2) (2 1 3) (1 2 3)
