Bug #1139

Status:
Closed
Priority:
Urgent
Category:
enhancing/improving
Target version:
Start date:
12 Dec 2017
Due date:
% Done:

100%

Estimated time:
1.51 h
Spent time:

Description

There are still problems with radical: sometimes it gives an empty list instead of an ideal.

```/**/ I := ideal(x^2, x*y+1);
[]
```

Related issues

Related to CoCoA-5 - Bug #1133: Radical bugClosed2017-12-01

History

#2 Updated by John Abbott7 months ago

The problem seems to be when the ideal contains 1.

```/**/ radical(ideal(x/x));
[]
```

#3 Updated by John Abbott7 months ago

Here is another case where things go wrong:

```/**/ use QQ[x,y,z,t];
/**/ I := ideal(2*x*y*z +2*y*t,  -y^3 -x*y*t +x*t^2,  x^2*z +2*x*y*z +y^2*t);
-->  ERROR: I don't know how to evaluate operator + between IDEAL and LIST
-->  WHERE: at line 1105 (column 19) of radical.cpkg5
```

#4 Updated by John Abbott7 months ago

Much like the example above:

```I := ideal(-x^3 -x*y^2 -x^2,  x^2*z -x^2 +y^2,  -x^2*t +x*t^2 -x*t);
I := ideal(y*z^3 +y^2*z*t,  x^2*z +2*y^2,  -x*y*t +y*z);
```

#5 Updated by Anna Maria Bigatti7 months ago

another

```/**/ I := ideal(x*(x^2 -y -x),  x^2*z  +y, t);
```

#6 Updated by Anna Maria Bigatti7 months ago

• Status changed from New to Closed
• Assignee set to Anna Maria Bigatti
• % Done changed from 0 to 100
• Estimated time set to 1.51 h

Fixed: all the problem was in ideal(1).
(there is a naughty trick in `ElimRedundant(E)`)
Now `radical(I)` exits `I` immediately if IsOne(I).

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