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 Post subject: qring of an nc_algebra
PostPosted: Mon Jan 22, 2018 9:13 pm 
I am running the following code in the "Try Online" section of the website (running version 4.1.0) from Nov. 2016:

Code:
LIB "nctools.lib";
ring A = 0,(a,b),dp;
def S = nc_algebra(-1,0);
setring S;
b^2==0;
ideal I = a^2;
qring R = twostd(I);
setring R;
b^2==0;


The first call of b^2==0 (after setring S) returns 0 (false), whereas the second call of b^2==0 (after setring R) yields 1 (true). I don't understand why this is the case, since b^2 is not be in the ideal generated by a^2. Am I doing something wrong?


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 Post subject: Re: qring of an nc_algebra
PostPosted: Thu Feb 01, 2018 11:55 am 

Joined: Wed May 25, 2005 4:16 pm
Posts: 190
No, nothing wrong: you found a bug in Singular.
The test for being a SCA ring had a bug.
It is now fixed in the sources with
https://github.com/Singular/Sources/commit/4fd796a9c41904bd840bcc8a2691b4dac9865de4


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