Common Lisp vs Java

I’ve been sort of wanting to learn LISP for long time (~ 10 years). Now finally I got some chance to try that out. I’ve started reading On Lisp by Paul Graham along with Practical Common Lisp by Peter Seibel. I find them pretty invaluable in learning Lisp.

It has been nearly 9 years since I’ve started learning Java, during my programming adventures, I’ve used COBOL, Perl and Ruby. But never got to build a complete application purely using functional programming. Partly inspired by on The Reinvigorated Programmer, I start my journey of learning Common Lisp.

I’m trying to compare how I do things in Java with the exercises/programs I write while learning Lisp. Here’s the first installment:

The following Common Lisp created a database of CDs with some data, and provides methods to store the database to a file and load the same from the file.

First the Common Lisp program:

(defvar *db* nil)

(defun make-cd (title artist rating ripped)
  (list :title title :artist artist :rating rating :ripped ripped))

(defun add-record (cd) (push cd *db*))

(defun prompt-read (prompt)
  (format *query-io* "~a: " prompt)
  (force-output *query-io*)
  (read-line *query-io*))

(defun dump-db ()
  (dolist (cd *db*)
    (format t "~{~{~a:~10t~a~%~}~%}" cd)))

(defun prompt-for-cd ()
  (make-cd
   (prompt-read "Title")
   (prompt-read "Artist")
   (or (parse-integer (prompt-read "Rating") :junk-allowed t) 0)
   (y-or-n-p "Ripped [y/n]:")))

(defun add-cds ()
  (loop (add-record (prompt-for-cd))
     (if (not (y-or-n-p "Another? [y/n]:")) (return))))

(defun save-db (filename)
  (with-open-file (out filename
		       :direction :output
		       :if-exists :supersede)
    (with-standard-io-syntax
      (print *db* out))))

(defun load-db (filename)
  (with-open-file (in filename)
    (with-standard-io-syntax
      (setf *db* (read in)))))

(defvar *db* nil)

(defun make-cd (title artist rating ripped)

(list :title title :artist artist :rating rating :ripped ripped))

(defun add-record (cd) (push cd *db*))

(defun prompt-read (prompt)

(format *query-io* "~a: " prompt)

(force-output *query-io*)

(read-line *query-io*))

(defun dump-db ()

(dolist (cd *db*)

(format t "~{~{~a:~10t~a~%~}~%}" cd)))

(defun prompt-for-cd ()

(make-cd

(prompt-read "Title")

(prompt-read "Artist")

(or (parse-integer (prompt-read "Rating") :junk-allowed t) 0)

(y-or-n-p "Ripped [y/n]:")))

(defun add-cds ()

(loop (add-record (prompt-for-cd))

(if (not (y-or-n-p "Another? [y/n]:")) (return))))

(defun save-db (filename)

(with-open-file (out filename

:direction :output

:if-exists :supersede)

(with-standard-io-syntax

(print *db* out))))

(defun load-db (filename)

(with-open-file (in filename)

(with-standard-io-syntax

(setf *db* (read in)))))

And here’s the Java version (without saving and reading from file).

Database.java

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;

public class Database {
    List cdList;

    public Database() {
        cdList = new ArrayList();
    }

    public Database(List cdList) {
        this.cdList = cdList;
    }

    public void addRecord(CompactDisc cd ) {
        cdList.add(cd);
    }

    public void dump(){
        for (CompactDisc compactDisc : cdList) {
            System.out.println("Title: " + compactDisc.getTitle());
            System.out.println("Artist: " + compactDisc.getArtist());
            System.out.println("Rating: " + compactDisc.getRating());
            System.out.println("Ripped: " + compactDisc.isRipped());
            System.out.println("---------------------------");
        }
        System.out.println("Total Items: " + cdList.size());
    }

    public void save(String path){
        try {
            PrintWriter fileWriter = new PrintWriter(
                                                   new FileOutputStream(path)
                                                   );

        } catch (FileNotFoundException e) {
            e.printStackTrace();

        }
    }

}

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.PrintWriter;

import java.util.ArrayList;

import java.util.List;

public class Database {

List cdList;

public Database() {

cdList = new ArrayList();

}

public Database(List cdList) {

this.cdList = cdList;

}

public void addRecord(CompactDisc cd ) {

cdList.add(cd);

}

public void dump(){

for (CompactDisc compactDisc : cdList) {

System.out.println("Title: " + compactDisc.getTitle());

System.out.println("Artist: " + compactDisc.getArtist());

System.out.println("Rating: " + compactDisc.getRating());

System.out.println("Ripped: " + compactDisc.isRipped());

System.out.println("---------------------------");

}

System.out.println("Total Items: " + cdList.size());

}

public void save(String path){

try {

PrintWriter fileWriter = new PrintWriter(

new FileOutputStream(path)

);

} catch (FileNotFoundException e) {

e.printStackTrace();

}

CompactDisc.java

public class CompactDisc {

    public CompactDisc() {
    }

    public CompactDisc(String title,
                                     String artist,
                                      int rating,
                                       boolean ripped) {
        this.title = title;
        this.artist = artist;
        this.rating = rating;
        this.ripped = ripped;
    }

    private String title;
    private String artist;
    private int rating;
    private boolean ripped;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getArtist() {
        return artist;
    }

    public void setArtist(String artist) {
        this.artist = artist;
    }

    public int getRating() {
        return rating;
    }

    public void setRating(int rating) {
        this.rating = rating;
    }

    public boolean isRipped() {
        return ripped;
    }

    public void setRipped(boolean ripped) {
        this.ripped = ripped;
    }
}

public class CompactDisc {

public CompactDisc() {

}

public CompactDisc(String title,

String artist,

int rating,

boolean ripped) {

this.title = title;

this.artist = artist;

this.rating = rating;

this.ripped = ripped;

}

private String title;

private String artist;

private int rating;

private boolean ripped;

public String getTitle() {

return title;

}

public void setTitle(String title) {

this.title = title;

}

public String getArtist() {

return artist;

}

public void setArtist(String artist) {

this.artist = artist;

}

public int getRating() {

return rating;

}

public void setRating(int rating) {

this.rating = rating;

}

public boolean isRipped() {

return ripped;

}

public void setRipped(boolean ripped) {

this.ripped = ripped;

}

Main.java

import java.util.Scanner;

public class Main {

    public static void main(String... args) {
        Database db = new Database();
        Scanner input = new Scanner(System.in);
        String inputString;

        while (true) {

            CompactDisc cd = new CompactDisc();
            System.out.print("Title: ");
            cd.setTitle(input.nextLine());

            System.out.print("Artist: ");
            cd.setArtist(input.nextLine());

            System.out.print("Rating: ");
            cd.setRating(Integer.valueOf(input.nextLine()));

            System.out.print("Ripped [y/n]: ");
            inputString = input.nextLine();
            if (inputString.equals("y")) {
                cd.setRipped(true);
            } else if (inputString.equals("n")) {
                cd.setRipped(false);
            } else {
                System.out.println("Invalid ripped status, setting it to false!");
            }

            db.addRecord(cd);

            System.out.print("Enter another ? [y/n]: ");
            inputString = input.nextLine();
            if(inputString.equalsIgnoreCase("n")){
                break;
            }
        }

        db.dump();

    }

}

import java.util.Scanner;

public class Main {

public static void main(String... args) {

Database db = new Database();

Scanner input = new Scanner(System.in);

String inputString;

while (true) {

CompactDisc cd = new CompactDisc();

System.out.print("Title: ");

cd.setTitle(input.nextLine());

System.out.print("Artist: ");

cd.setArtist(input.nextLine());

System.out.print("Rating: ");

cd.setRating(Integer.valueOf(input.nextLine()));

System.out.print("Ripped [y/n]: ");

inputString = input.nextLine();

if (inputString.equals("y")) {

cd.setRipped(true);

} else if (inputString.equals("n")) {

cd.setRipped(false);

} else {

System.out.println("Invalid ripped status, setting it to false!");

}

db.addRecord(cd);

System.out.print("Enter another ? [y/n]: ");

inputString = input.nextLine();

if(inputString.equalsIgnoreCase("n")){

break;

}

db.dump();

}

This is not one-to-one comparison between Common Lisp version and Java version, this is just part of my note taking while learning LISP and wrap my head around a new language.

Posted in: Programming

java

lisp

Programming

shane smith says:

March 18, 2010 at 7:42 am

nice work :-)

- Vijay Kiran says:
  
  March 18, 2010 at 8:41 pm
  
  Thanks :-)
  
shane smith says:

March 18, 2010 at 7:42 am

nice work :-)

- Vijay Kiran says:
  
  March 18, 2010 at 8:41 pm
  
  Thanks :-)
  
shane smith says:

March 18, 2010 at 7:42 am

nice work :-)

Vijay Kiran says:

March 18, 2010 at 8:41 pm

Thanks :-)

Vijay Kiran says:

March 18, 2010 at 8:41 pm

Thanks :-)

Mike Taylor says:

March 19, 2010 at 8:20 pm

Vijay, I am delighted and humbled that my own noodlings have been some small part of pushing you over the edge into learning Lisp. Hopefully I will start to catch up with you soon :-)

Mike Taylor says:

March 19, 2010 at 8:20 pm

Vijay, I am delighted and humbled that my own noodlings have been some small part of pushing you over the edge into learning Lisp. Hopefully I will start to catch up with you soon :-)

Mike Taylor says:

March 19, 2010 at 8:20 pm

Vijay, I am delighted and humbled that my own noodlings have been some small part of pushing you over the edge into learning Lisp. Hopefully I will start to catch up with you soon :-)

Mike Taylor says:

March 19, 2010 at 8:20 pm

Vijay, I am delighted and humbled that my own noodlings have been some small part of pushing you over the edge into learning Lisp. Hopefully I will start to catch up with you soon :-)

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