Not so Quine

Daniele Olmisani - daniele.olmisani@gmail.com, see LICENSE file.

main(p){printf(p="main(p){printf(p=%c%s%1$c,34,p);}",34,p);}

by Dario Dariol

A quine is a non-empty computer program which takes no input and produces a copy of its own source code as its only output. Wikipedia

C++ Quines

Compile using:

$ g++ -std=c++17 quine.cpp -o quine

Verify using:

$ ./quine | diff quine.cpp -

My signature

Please, refer to quine.cpp:

auto s = R"(
#include <iostream>
main() {
  std::cout << "auto s = R\"(" << s << ")\";" << s;
}
)";
#include <iostream>
main() {
  std::cout << "auto s = R\"(" << s << ")\";" << s;
}

An other try

Please, refer to quine3.cpp:

#include<cstdio>
int main(){char n[]=R"(#include<cstdio>
int main(){char n[]=R"(%s%c";printf(n,n,41);})";printf(n,n,41);}

An other try

Please, refer to quine2.cpp:

#include <iostream>
#include <string>

std::string s = R"(
#include <iostream>
#include <string>

std::string s = R"(
";

int main() {
  std::cout << s.replace(59, 1, s+')');
  return 0;
}
)";

int main() {
  std::cout << s.replace(59, 1, s+')');
  return 0;
}

An other try

Please, refer to quine1.cpp:

#include <iostream>
#include <iomanip>

int main() {
  const char *s[] = {
    "    ",
    "#include <iostream>",
    "#include <iomanip>",
    "",
    "int main() {",
    "  const char *s[] = {",
    "  };",
    "  for(int i = 1; i < 6; ++i)",
    "    std::cout << s[i] << std::endl;",
    "  for(int i = 0; i < 15; ++i)",
    "    std::cout << s[0] << std::quoted(s[i]) << ',' << std::endl;",
    "  for(int i = 6; i < 15; ++i)",
    "    std::cout << s[i] << std::endl;",
    "  return 0;",
    "}",
  };
  for(int i = 1; i < 6; ++i)
    std::cout << s[i] << std::endl;
  for(int i = 0; i < 15; ++i)
    std::cout << s[0] << std::quoted(s[i]) << ',' << std::endl;
  for(int i = 6; i < 15; ++i)
    std::cout << s[i] << std::endl;
  return 0;
}

Other Quines

Other interesting quines.

Rust

fn main(){print!("{}{0:?})}}","fn main(){print!(\"{}{0:?})}}\",")}

Python 3

_='_=%r;print(_%%_)';print(_%_) 

In Python the expression "name: %s" % value performs a string formatting similar to the C printf function. The %r formatter addes single quotes around the value and the double %% sign is an escaping sequence of the character %.

APL

A trivial quine in APL is given by any expression:

0

that will be output printed as result.

Instead, an interisting and non-trivial quine is

1⌽,⍨9⍴'''1⌽,⍨9⍴'''

Try the code in TryAPL

Let's we will trying to understand.

APL expressions are evaluated right-to-left, so starting from the end

'''1⌽,⍨9⍴'''

is evaluated as

'1⌽,⍨9⍴'

because ''' is an escaped single quote.

then

9⍴'''1⌽,⍨9⍴'''

is evaluated as

'1⌽,⍨9⍴''

because 9⍴ will add a new element at the end of the 8 charater length string (repeting the string as needed).

then

,⍨9⍴'''1⌽,⍨9⍴'''

is evaluated as

'1⌽,⍨9⍴'''1⌽,⍨9⍴''

because ,⍨ will append its argument to itself (comma is the append operator, while ⍨ will duplicate the right argument as left argument).

then

1⌽,⍨9⍴'''1⌽,⍨9⍴'''

is evaluated as

1⌽,⍨9⍴'''1⌽,⍨9⍴'''

because 1⌽ will rotate the right argument of one position (left argument).

CBM BASIC

Classic cheat.

1 LIST

A quine in CBM BASIC v2 that should be edited directly in a real Commodore 64.

Bit boring, but an actual quine.

1 READA$:PRINTA$CHR$(34)A$:DATA"1 READA$:PRINTA$CHR$(34)A$:DATA

Without any trick (just a little trouble in entering the last character, just go cursor back on the first char and press RETURN):

1 READA$:PRINTA$CHR$(34)A$CHR$(34):DATA"
1 READA$:PRINTA$CHR$(34)A$CHR$(34):DATA"

Natural Language

A quine using natural language.