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Self-writing program

Submitted by Kestrel on Mon, 2006-02-20 01:25
Folks,\\There is an interesting programming problem that was one of the coolest puzzles I took in CS courses. It is about whether you can write a program that writes itself upon execution!\\That is, if the source code is something like that (pseudo-code) {{{ Begin Print(“Something ……”) End }}} The output after execution should be exactly that same! {{{ Begin Print(“Something ……”) End }}} Now, java gurus! who’s gonna provide us with a java program that writes itself? :) \\ Note that the program should not accept any inputs (reading some file or accepting user inputs)
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Here it is

Submitted by Amr on Mon, 2006-02-20 10:03.
Here it is: Instructions *Creat a java file named SelfWriter.java, and paste the following line on it *compile using JDK 1.5, for the printf function *solution is in one line, to save some \n :D *after execution, copy the output to the java file under that line, to compare {{{ package myPack;public class SelfWriter {public static void main(String[]args){StringBuffer a = new StringBuffer();System.out.printf(a.append("package myPack;public class SelfWriter {public static void main(String[]args){StringBuffer a = new StringBuffer();System.out.printf(a.append(%c%s%c).toString(),34,a,34);}}").toString(),34,a,34);}} }}} ------------- Amr Kourany Software Engineer IBM WTC, Egypt Branch
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the code provided seems to

Submitted by Kestrel on Mon, 2006-02-20 12:08.
the code provided seems to be okay but the explanation is not!\\ What do you mean by "to save some \n!"
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Anthor Version

Submitted by Amr on Mon, 2006-02-20 12:56.
Here is a version with new lines, as u see, the printf is full of \n and \t, and that's what i wanted to save, beside comparasion now is quiet difficult. {{{ package myPack; public class SelfWriter { public static void main(String[]args) { StringBuffer a = new StringBuffer(); System.out.printf(a.append("package myPack;%cpublic class SelfWriter {%c%cpublic static void main(String[]args) {%c%c%cStringBuffer a = new StringBuffer();%c%c%cSystem.out.printf(a.append(%c%s%c).toString(),13,13,9,13,9,9,13,9,9,34,a,34,13,9,13);%c%c}%c}").toString(),13,13,9,13,9,9,13,9,9,34,a,34,13,9,13); } } }}} ------------- Amr Kourany Software Engineer IBM WTC, Egypt Branchb
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I got your point now.

Submitted by Kestrel on Mon, 2006-02-20 13:13.
I got your point now.\\ Okay now what is the minimum number of code (in terms of chars) that would do that?
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May be...

Submitted by Amr on Mon, 2006-02-20 13:41.
We can get ride of the StringBuffer and make use of args, but there must be at least one argument passed to the program. code will be like this {{{ public class myClass { public static void main(String[]args) { System.out.printf(args[0]=new String("public class SelfWriter {%c%cpublic static void main(String[]args) {%c%c%System.out.printf(args[0]=new String(%c%s%c).toString(),13,9,13,9,9,13,9,9,34,args[0],34,13,9,13);%c%c}%c}").toString(),13,9,13,9,9,13,9,9,34,args[0],34,13,9,13); } } }}} and u will use the default package and of course u wil get ride of all the \n \t ------------- Amr Kourany Software Engineer IBM WTC, Egypt Branchb
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replacing StringBuffer a

Submitted by Kestrel on Tue, 2006-02-21 00:32.
replacing StringBuffer a with args[0] won't decrease the size becasue you have to replace every a with args[0] \\ Removing the package is quite good. Can't you remove the public too?\\ Now we have Amr's solution with 322 bytes code.\\ Can you do better guys ?
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Smaller Version

Submitted by Amr on Tue, 2006-02-21 09:33.
This version is 201 bytes only {{{ class S{public static void main(String[]x){String a;System.out.printf(a=new String("class S{public static void main(String[]x){String a;System.out.printf(a=new String(%c%s%c),34,a,34);}}"),34,a,34);}} }}} ------------- Amr Kourany Software Engineer IBM WTC, Egypt Branchb
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Perfect! The file is even

Submitted by Kestrel on Wed, 2006-02-22 07:05.
Perfect! \\ The file is even 200 bytes! This is better than the shortest class that i am aware of.\\ Those types of programs are called Quines. A Quine \\"http://en.wikipedia.org/wiki/Quine" is a program that produces its\\ complete source code as its only output.\\ Any programming language that is turing complete \\"http://en.wikipedia.org/wiki/Turing-complete" which is able \\ to output any string has a quine program.\\ For example it has been proved that XSLT 1.0 is turing complete \\ "http://www.unidex.com/turing/utm.htm" thus there should be some quine \\xsl "http://w3log.server-wg.de/000016.html" \\
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