Shortest Ruby Quine

Shortest Ruby Quine

Unfortunately RubyGarden doesn't exist anymore. Here are a couple of links to make up for it (the one Kevin posted is not the shortest one anymore by the way):

The first quines in Ruby

s="s=%c%s%c; printf s,34,s,34,10%c"; printf s,34,s,34,10

ruby quine slightly smaller than python quine

_="_=%p;puts _%%_";puts _%_

shortest nozero [sic!] ruby quine

puts <<2*2,2
puts <<2*2,2
2

Ruby: Print source code

A Quine is a program that prints out its own source code as its only functionality and yes you can do this without reading the source code file. The real challenge, and fun, is to write as short a Quine as possible.

The above would not be a Quine because it doesn't print its own source code out and it couldn't be because it does more than just output its own code.

Check out this thread:

Shortest Ruby Quine

Explanation for perl quine

Look at printf parameters and substitute them by hand,

(39 is single quote, ', and 10 is newline \n when interpreted as %c)
so $a which start as

$a=%c%s%c;printf($a,39,$a,39,10);%c

becomes (replaced chars marked below with ^)

$a='%s%c;printf($a,39,$a,39,10);%c
   ^ (first %c replaced)
$a='$a=%c%s%c;printf($a,39,$a,39,10);%c%c;printf($a,39,$a,39,10);%c
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (%s replaced)
$a='$a=%c%s%c;printf($a,39,$a,39,10);%c';printf($a,39,$a,39,10);%c
                                       ^ (second %c replaced)

and finally

$a='$a=%c%s%c;printf($a,39,$a,39,10);%c';printf($a,39,$a,39,10);\n
                                             (last %c replaced) ^^ 

Output Ruby class

Sure. You can use the magic constant __FILE__ which contains the path to the file that you use it in:

class MyClass
  def initialize
    puts File.read(__FILE__)
  end
end

This will print the contents of the file containing the definition of MyClass every time you create a MyClass object.

What are quines? Any specific purpose to have them?

Quines are useless in a practical sense, but they're a great exercise to help you learn more about a language.

Here's a very concise one in python:

a='a=%r;print a%%a';print a%a

Can a program output a copy of itself

Yes. A programme that can make a copy of itself is called a "quine".

The basic idea of most quines is:

1. You write code that takes a string literal s and prints it, while replacing occurrences (or the occurrence) of a special substring foo in s by the value of s itself.

2. You take the entire source code of the program so far and use it as the definition for s. but you exclude the definition of s from the string, instead replacing it by foo.

That's the general idea. The rest is string formatting details, really.

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