[Retros] Retractor 2.0 now available online
Thierry LE GLEUHER
t.legleuher at hotmail.fr
Mon Apr 12 12:51:49 EDT 2021
Very good news.
I was just going to begin to work on that subject, but now the job is down.
Thank you very much.
De : Retros <retros-bounces at janko.at> de la part de Theodore Hwa <hwatheod at cs.stanford.edu>
Envoyé : samedi 10 avril 2021 07:56
À : retros at janko.at <retros at janko.at>
Objet : [Retros] Retractor 2.0 now available online
Hello retro enthusiasts,
Retractor 2.0 is now available online as an application in your browser at
For those not familiar, Retractor is a program for exploring retro
problems. It lets you setup a position and play backwards from it, and
warns you if it detects an illegal position. It reports the number of
captures and promotions in a position. It can also solve some "Last N
For those of you who have been around this list for a while, Retractor 2.0
is the successor of Retractor 1.0 which was a Windows application
developed by myself and Chad Whipkey in 1998.
Right now, Retractor 2.0 is pretty much a straight port of Retractor 1.0
immediate items for improvement are (1) taking promotions into account
when counting pawn captures, and (2) a more general method for detection
of illegal retro-cages (right now, some common cases are hard-coded).
I am using the "Last Single Move" problems (types A-D) at
https://www.janko.at/Retros/Records/LastMove/index.htm as benchmarks for
improving Retractor. When going through those problems, I found that when
Retractor cannot solve one of them, it's usually because of (1) and/or
If you are interested in the source code, it is available on github at:
Any and all feedback, comments, contributions for Retractor are
appreciated! You can contact me at this email address, or on the github
Retros mailing list
Retros at janko.at
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