This repository consists mainly of two Python scripts. The first is a self-replicating program, often termed a quine, in honor of the American logician W. Quine (1908-2000). The second is a module for checking whether a given Python script is a quine.
The quine.py script prints its own source code when executed and returns
None. It consists of the composition of two functions, called g and f.
The function g accepts an arbitrary string w as an argument and performs the
following steps:
- Prints the definition of another function, having no parameters, that
returns
wwhen called. (Explicitly, the latter is justlambda: w.) - Prints the string
w. - Prints the string
"g(f())".
In turn, the function f is a particular case of the function described in
step 1 where w is taken to be the full definition of g. Thus, f is a
function of no parameters which simply returns the source code of g as a string.
When the call g(f()) is run, f provides the source code of g as the
argument of g, which triggers the printing of the definitions of f and g,
along with with the expression "g(f())", which collectively make up the
script's own source code.
The quine_checker.py module contains utility functions for reading the contents
of another script, capturing its output, comparing the two, and finally reporting
whether that script is a quine.
The program run_quine_check simply calls quine_checker on the candidate
whose filename is provided as its argument.
Place the Python script you want to check, say, quine_candidate.py, in the
directory where the files in the repository are stored. Then run the
the following command in the terminal:
python3 run_quine_check.py quine_candidate.py
This will output a report on whether the script is a quine, along with other relevant information.
Contributions are welcome. Please feel free to submit a pull request.