Quine¶

A quine is a program that prints itself. programs/quine16.fj is the FlipJump quine — and it’s a particularly interesting one because of how the language defines “self”.

What “self” means here¶

Most quines print their source code. The FlipJump quine prints its compiled binary (the .fjm file, including the .fjm header struct) — verbatim, byte-for-byte. The file’s own header comment is explicit:

“I took the liberty to define a Quine for FlipJump as a binary (fjm) that prints itself (including the header struct).”

Why pick the binary? FlipJump’s “source code” is ambiguous: a FlipJump program is fundamentally a stream of (flip_address, jump_address) pairs, and that stream can be represented as text, as packed binary, or in many other formats. The binary .fjm is the canonical representation that any conforming interpreter accepts, so quining the binary is the most language-invariant choice.

Why it’s notable¶

FlipJump is self-modifying by design — every variable is implemented by modifying its own jump addresses at runtime. The quine extends that to the whole program: by the time stl.output finishes, the program has read its own bytes (from program memory!) and emitted them to stdout. The “data table” of conventional quines is replaced by program memory itself.

Try it¶

The upstream file’s header comment shows the exact incantation:

fj --asm -w 16 quine16.fj -o quine16.fjm    # assemble (16-bit word width is required)
fj --run -s quine16.fjm > /tmp/output       # run, capture stdout
diff quine16.fjm /tmp/output                 # should produce NO output if it's truly a quine
echo "quine!"                                # confirmation

The -w 16 is mandatory: the program is hand-tuned for 16-bit words, so it doesn’t work at the default 64-bit width.

The author¶

The FlipJump quine is by Luis Fernando Estrozi. The source file is ~1000 lines, most of which is comments explaining the construction — well worth reading for anyone interested in self-reference under unusual computational models.