Print your own code.

[Magnus L. Hetland]

François Pinard <pinard at iro.umontreal.ca> writes:

> nascheme at ucalgary.ca (Neil Schemenauer) writes:
> 
> > >I heard that it's possible to write a python script that prints
> > >it's own source... is that true? How?
> 
> > That is an old trick.  I believe it can be done in almost any
> > language.
> 
> There is an old theorem by Kleene about this (the fixed-point theorem).  Gosh,
> this is really far in my memory -- no idea of what the theorem really says :-)

Being one of the (probably many) people who have done this in Python,
I would be quite interested in the theorem...

And - it is called quineing or something... And there is a web-page
for it somewhere... Oh, well. My version is:

python -c "x='python -c %sx=%s; print
x%%((chr(34),repr(x),chr(34))%s'; print x%(chr(34),repr(x),chr(34))"


Run it on the command-line (without the line break in the middle) and
your outpur should equal the comman. (This, of course, includes the
"python -c" bit...)

--

  Magnus
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