1 | initial version |

This works for me in 4.6.2:

```
sage: A = matrix(QQ, 2, 2, [3,9,6,10])
sage: block_matrix([ [A, -A], [~A, 100*A] ])
[ 3 9| -3 -9]
[ 6 10| -6 -10]
[-----------+-----------]
[-5/12 3/8| 300 900]
[ 1/4 -1/8| 600 1000]
```

Previously I think you had to write

```
sage: A = matrix(QQ, 2, 2, [3,9,6,10])
sage: block_matrix([A, -A, ~A, 100*A])
[ 3 9| -3 -9]
[ 6 10| -6 -10]
[-----------+-----------]
[-5/12 3/8| 300 900]
[ 1/4 -1/8| 600 1000]
```

or at least you did back in 4.5.1, and it looks like the constructor was rewritten not so long ago. Check your block_matrix's help.

2 | No.2 Revision |

This works for me in 4.6.2:

```
sage: A = matrix(QQ, 2, 2, [3,9,6,10])
sage: block_matrix([ [A, -A], [~A, 100*A] ])
[ 3 9| -3 -9]
[ 6 10| -6 -10]
[-----------+-----------]
[-5/12 3/8| 300 900]
[ 1/4 -1/8| 600 1000]
```

Previously I think you had to write

```
sage: A = matrix(QQ, 2, 2, [3,9,6,10])
sage: block_matrix([A, -A, ~A, 100*A])
[ 3 9| -3 -9]
[ 6 10| -6 -10]
[-----------+-----------]
[-5/12 3/8| 300 900]
[ 1/4 -1/8| 600 1000]
```

or at least you did back in 4.5.1, and it looks like the constructor was rewritten not so long ago. Check your block_matrix's ~~help.~~help.. or upgrade, I guess. :^)

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