1 | initial version |

This is definitely a bug, thanks for reporting! As you can see in the source code:

```
sage: QQbar.__contains__??
```

the test:

```
`elif EQ:`
```

which corresponds to:

```
sage: bool(I == QQbar(I))
```

leads to:

```
TypeError: unsupported operand parent(s) for +: 'Number Field in I with defining polynomial x^2 + 1' and 'Algebraic Field'
```

which is catched to return `False`

.

I have opened trac ticket 24209 for this.

2 | No.2 Revision |

This is definitely a bug, thanks for reporting! As you can see in the source code:

```
sage: QQbar.__contains__??
```

the test:

` `~~`elif EQ:`
~~elif EQ:

which corresponds to:

```
sage: bool(I == QQbar(I))
```

leads to:

```
TypeError: unsupported operand parent(s) for +: 'Number Field in I with defining polynomial x^2 + 1' and 'Algebraic Field'
```

which is catched to return `False`

.

I have opened trac ticket 24209 for this.

3 | No.3 Revision |

This is definitely a bug, thanks for reporting! As you can see in the source code:

```
sage: QQbar.__contains__??
```

the test:

```
elif EQ:
```

which corresponds to:

```
sage: bool(I == QQbar(I))
```

leads to:

```
TypeError: unsupported operand parent(s) for +: 'Number Field in I with defining polynomial x^2 + 1' and 'Algebraic Field'
```

which is catched to return `False`

.

I have opened trac ticket 24209 for this.

**EDIT** This issue is fixed now (Sage 9.4-beta3):

```
sage: sqrt(-1) in QQbar
True
sage: I in QQbar
True
```

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