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Re: How I Learned About Quines

by ambrus (Abbot)
on Apr 16, 2010 at 11:45 UTC ( #835076=note: print w/replies, xml ) Need Help??

in reply to How I Learned About Quines

Apart from the webpages you mention, there's also Douglas Hofstadter's book Gödel, Escher, Bach. For perl specifically, there's my Short quines.

Update: These days I also started to like quines that look like this:

print+("\\","\"",",","print+(",")[3,1,0,0,1,2,1,0,1,1,2,1,2,1,2,1,3,1, +2,1,4,1,4]")[3,1,0,0,1,2,1,0,1,1,2,1,2,1,2,1,3,1,2,1,4,1,4]

Update 2010-01-28: These unpack quines by mtve below are nice. Here's my attempt.

print unpack a44X44a43xaXXaaXaXaxaXaX4axa, "print unpack a44X44a43xaXX +aaXaXaxaXaX4axa, \"\\\nn"

Or, if you don't need the newline, this works too.

print unpack a35X35a34xaXXaaXaXXa,"print unpack a35X35a34xaXXaaXaXXa,\ +"\\"

Update 2012-12-12: see also General quine, Short quines.

Replies are listed 'Best First'.
Re^2: How I Learned About Quines
by mtve (Deacon) on Mar 03, 2011 at 18:04 UTC

    uuencode to the rescue!

    print unpack a27uX30a30X3u,"print unpack a27uX30a30X3u,!(@"
      well duh, just to complement that never-ending unpack
      print pack'a*c3X2a*c4X2a2c4X3a2c3X3c3X2c2Xa3cXc2Xa3',("print pack'a*c3X2a*c4X2a2c4X3a2c3X3c3X2c2Xa3cXc2Xa3',(",34,44,")x7")x7

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[Eily]: you could tie a variable into not having the same value each time, if you like to make people who try to debug your code facepalm
[Corion]: perl -wle 'package o; use overload q("") => sub {warn "str"; ""}, bool => sub{warn "bool"; 1}; package main; my $o={}; bless $o => o; print "Yay" if ($o && !length($o))'
[Corion]: But people writing such code should document the objects they construct and why it makes sense for an object to be invisible as string while being true in a boolean context
[hippo]: That's equal parts clever and horrendous.
[Eily]: the overload version wouldn't return true with "$x" && !length $x though, I guess
[hippo]: The more I look at this code, the more $x is a plain old scalar and the more this condition will never be true. I'm calling it a bug at this point.
[hippo]: Thanks for your input which has soothed my sanity (a little)
[Corion]: Eily: Sure - if you force both things into stringy things, then you break that magic. But that would also mean that you changed the expression, as now $x = 0.00 will be true instead of false as it were before
[Corion]: Ah no, at least in my feeble experiments that doesn't change the meaning
[Corion]: We sell sanity in small packages ;)

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