Opened 13 years ago

Closed 13 years ago

# nc_algebra over qring should not be allowed

Reported by: Owned by: Oleksandr Oleksandr major 3-1-1 singular-kernel 3-1-0 nc, qring, ring, nc_algebra hannes

### Description

The point is that we need twosided GB in order to build a factor of general G-algebra, whereas the following example shows that we don't check whether the currRing is not a qring...

```> ring r;
> def gg = nc_algebra(-1, 1);
> setring gg; gg;
//   characteristic : 32003
//   number of vars : 3
//        block   1 : ordering dp
//                  : names    x y z
//        block   2 : ordering C
//   noncommutative relations:
//    yx=-xy+1
//    zx=-xz+1
//    zy=-yz+1
//   noncommutative type:0
//      is skew constant:1
//                 ncref:1
//               commref:1
//               baseref:1
> twostd(x);
_[1]=1

> setring r; qring q = std(x); q;
//   characteristic : 32003
//   number of vars : 3
//        block   1 : ordering dp
//                  : names    x y z
//        block   2 : ordering C
// quotient ring from ideal
_[1]=x
> def g = nc_algebra(-1, 1); setring g; g;
//   characteristic : 32003
//   number of vars : 3
//        block   1 : ordering dp
//                  : names    x y z
//        block   2 : ordering C
//   noncommutative relations:
//    yx=-xy+1
//    zx=-xz+1
//    zy=-yz+1
//   noncommutative type:0
//      is skew constant:1
//                 ncref:1
//               commref:1
//               baseref:1
// quotient ring from ideal
_[1]=x
```

Is there any way to disable a set of commands for qrings (e.g. nc_algebra)? If not - i will add such a test inside nc_CallPlural...

### comment:1 Changed 13 years ago by hannes

Resolution: → fixed new → closed

is fixed: def g = nc_algebra(-1, 1); setring g; g;

? basering must NOT be a qring! ? error occurred in or before STDIN line 6: `def g = nc_algebra(-1, 1); setring g; g;`

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