QCLDPCCodeFromGroup error (from gap-forum)

[dimpase]

Date: Fri, 12 Aug 2016 05:52:33 +0000 (UTC)
From: "R.N. Tsai" r_n_tsai@yahoo.com
as reported there:

To: GAP Forum forum@gap-system.org
Subject: [GAP Forum] Error using guava function QCLDPCCodeFromGroup

Dear Forum,
I tried to use the QCLDPCCodeFromGroup defined in the guava package :I used the example given in the documentation :

LoadPackage("guava","0",false);
C:=QCLDPCCodeFromGroup(7,2,3); 

I get this error :
Error, no method found! For debugging hints type ?Recovery from NoMethodFoundError, no 1st choice method found for `QCLDPCCodeFromGroup' on 3 arguments called from<function "HANDLE_METHOD_NOT_FOUND">(
+)
?QCLDPCCodeFromGroup returns the expected information about it, so it seems that gapknows about the function and I do load the guava package.
I'm using this version of GAP under windows.GAP 4.8.3, 19-Mar-2016, build of 2016-03-20 23:48:47 (GMTST)
I got the same error with win32 and win64 versions and under linux.
Thanks for your help,R.N.

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[fingolfin]

Indeed the guava manual talks about QCLDPCCodeFromGroup and uses it in several examples. As to the guava code, it declares QCLDPCCodeFromGroup as a GAP operation, but then doesn't install methods for it. Even the version shipped with GAP 4.5 has the same issue.

This is quite weird. Did the method installation for QCLDPCCodeFromGroup just got lost by accident at some point in the past? Or was it never realy implemented? Or is it avaiable, just under a different name?

[dimpase]

It looks as if it wasn't committed at all. Indeed,

d16b09e8 (Joe Fields 2014-03-23 17:03:59 -0400  41) Version 3.6 (06-2008):
d16b09e8 (Joe Fields 2014-03-23 17:03:59 -0400  42)    o Added QCLDPCCodeFromGroup function.

claims it's there already in the 2nd commit to repo.
But it's not there at that point.

[dimpase]

But its implementation is in the guava3.6 tarball at https://giam.southernct.edu/Guava/
So it can be obtained. Strange, indeed, it's not in the git repo.
I didn't check all the tarballs there, but it's present in version 3.6 and 3.7, but gone in 3.12

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clarification - it was removed in 3.9.

[dimpase]

I emailed Joe Fields, asking for an explanation.

[fingolfin]

Indeed, it was lost between 3.8 and 3.9. No mention of it in CHANGES.guava ?

Perhaps there was a reason and @osj1961 remembers... But if it was an accident, well, PR #77 adds it back.