## Bug #1191

### ApproxSolve: log(0) on some examples

Status:
Feedback
Priority:
High
Assignee:
Category:
bug
Target version:
Start date:
19 Jun 2018
Due date:
% Done:

90%

Estimated time:
Spent time:

Description

The following input attempts to compute log(0).

```use QQ[x,y,z];
L := [y^3 +x*z^2,  2*x^2*y -4*x*z^2 +3*x*y,  2*x^3 +x^2*y -2*z^3]; -- zero dim!
ApproxSolve(L);
```

### History

#### #1 Updated by John Abbott27 days ago

• Status changed from New to In Progress
• % Done changed from 0 to 10

Something odd must have happened: `ApproxSolve` is failing on almost trivial examples.
Here are some simpler failing examples:

```ideal(-2*x*y^2 +2*x^2 +3*x*y,  -3*y^3 -2*x^2);
```

```ideal(-x^2 +3*x*y -y,  -3*y^2 +x)
```

Maybe there is a problem when (0,0) is a solution?

#### #2 Updated by John Abbott27 days ago

It even fails in a univariate case... `-3*x^2+2*x`.
Investigating...

#### #3 Updated by John Abbott27 days ago

Here is a surprise:

```RealRoots(x); --> gives error log(0)
```

Ulrich has the version from Jan 2018, and his works...
So I must have made a recent change... sigh!

#### #4 Updated by John Abbott27 days ago

• Status changed from In Progress to Feedback
• Assignee set to John Abbott
• % Done changed from 10 to 90

The problem was caused by a new better impl of `RootBound` which can return zero (if arg is just `x`); the old `RootBound` could not do this.

Fixed.

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