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quine.md

@@ -2,16 +2,26 @@
 
 Quine is a nonempty [program](program.md) which prints its own source code. It takes no input, just prints out the [source code](source_code.md) when run (without [cheating](cheating.md) such as reading the source code file). Quine is basically a [self-replicating](self_replication.md) program, just as [in real world](irl.md) we may construct robots capable of creating copies of themselves (afterall we humans are such robots). The name *quine* refers to the philosopher Willard Quine and his paradox that shows a structure similar to self-replicating programs. Quine is one of the standard/[fun](fun.md)/[interesting](interesting.md) programs such as [hello world](hello_world.md), [compiler bomb](compiler_bomb.md), [99 bottles of beer](99_bottles.md) or [fizzbuzz](fizzbuzz.md).
 
-From [mathematical](math.md) point of view quine is a fixed point of a [function](function.md) (not to be confused with [fixed_point arithmetic](fixed_point.md)) represented by the [programming language](programming_language.md). I.e. if we see the programming language as a function f(x), where *x* is source code and the function's output is the program's output, quine is such *x* that *f(x) = x*.
+From [mathematical](math.md) point of view quine is a fixed point of a [function](function.md) (not to be confused with [fixed_point arithmetic](fixed_point.md)) represented by the [programming language](programming_language.md). I.e. if we see the programming language as a function f(x), where *x* is source code and the function's output is the program's output, quine is such *x* that *f(x) = x*. **A quine can be written in any [Turing complete](turing_completeness.md) [language](programming_language.md)**, the proof comes from the *fixed point theorem* (which says functions satisfying certain conditions always have a fixed point, i.e. a quine).
 
-Similar efforts include e.g. making self matching [regular expressions](regex.md) (for this task to be non-trivial the regex has to e.g. be enclosed between `/`s). Yet another similar challenge is a [polyglot](polyglot.md) program -- one that is a valid program in several languages -- some programs can be quines and polyglots at the same time, though these are super hard to make.
+Similar efforts include e.g. making self matching [regular expressions](regex.md) (for this task to be non-trivial the regex has to e.g. be enclosed between `/`s). Yet another similar challenge is a [polyglot](polyglot.md) program -- one that is a valid program in several languages -- some programs can be quines and polyglots at the same time, i.e. **polyglot quines**.
 
-Quine can be written in any [Turing complete](turing_completeness.md) [language](programming_language.md) (according to [Wikipedia](wikipedia.md)), the challenge is in the [self reference](self_reference.md) -- normally we cannot just single-line print a string literal containing the source because that string literal would have to contain itself, making it [infinite](infinity.md) in length. The idea commonly used to solve this problem is following:
+The challenge of creating quines is in the [self reference](self_reference.md) -- normally we cannot just single-line print a string literal containing the source because that string literal would have to contain itself, making it [infinite](infinity.md) in length. The idea commonly used to solve this problem is following:
 
 1. On first line start a definition of string *S*, later copy-paste to it the string on the second line.
 2. On second line put a command that prints the first line, assigning to *S* the string in *S* itself, and then prints *S* (the second line itself).
 
-This is a quine in [C](c.md):
+Yet a stronger quine is so called **radiation hardened quine**, a quine that remains quine even after any one character from the program has been deleted (found here in [Ruby](ruby.md): https://github.com/mame/radiation-hardened-quine). Other plays on the theme of quine include e.g. a program that produces a bigger program which will again produce yet bigger program etc.
+
+Another extension of a quine is **multiquine** -- this is NOT a polyglot quine! Multiquine is a quine written in some programming language *L0*; under normal circumstances this program behaves like a normal quine, but it has an extra feature: when passed a parameter *N* (e.g. through [CLI](cli.md) flag or through standard input), it will print a program in another language, *LN*, which itself is this multiquine (so it can again be used to get back the program in *L0* and so on). I.e. a multiquine is a quine which can switch between several languages.
+
+In the [Text](plaintext.md) [esoteric programming language](esolang.md) every program is a quine (and so also a radiation hardened one).
+
+## List Of Quines
+
+**Brainfuck**: not short, has over 2100 characters.
+
+**[C](c.md)**:
 
 ```
 #include <stdio.h>
@@ -19,24 +29,26 @@ char s[] = "#include <stdio.h>%cchar s[] = %c%s%c;%cint main(void) { printf(s,10
 int main(void) { printf(s,10,34,s,34,10,10); return 0; }
 ```
 
-This is a quine in [Python](python.md):
+**[comun](comun.md)**:
+
+```
+0 46 32 34 S 34 32 58 83 S --> S: "0 46 32 34 S 34 32 58 83 S --> " .
+```
+
+**[Python](python.md)**:
 
 ```
 s="print(str().join([chr(115),chr(61),chr(34)]) + s + str().join([chr(34),chr(10)]) + s)"
 print(str().join([chr(115),chr(61),chr(34)]) + s + str().join([chr(34),chr(10)]) + s)
 ```
 
-This is a quine in [comun](comun.md):
+**text**:
 
 ```
-0 46 32 34 S 34 32 58 83 S --> S: "0 46 32 34 S 34 32 58 83 S --> " .
+This is a quine in text.
 ```
 
-TODO: more langs?
-
-Yet a stronger quine is so called *radiation hardened quine*, a quine that remains quine even after any one character from the program has been deleted (found here in [Ruby](ruby.md): https://github.com/mame/radiation-hardened-quine). Other plays on the theme of quine include e.g. a program that produces a bigger program which will again produce yet bigger program etc.
-
-In the [Text](plaintext.md) [esoteric programming language](esolang.md) every program is a quine (and so also a radiation hardened one).
+TODO: more, make biquine of C and comun
 
 ## See Also