new of from for MutableMatrices

[kschwede]

I noticed that the new of from syntax sometimes has unexpected consequences (I can understand why it happens, but maybe it shouldn't?)

In particular, if M is a MutableMatrix and I write N = new MutableMatrix from M then if I change an entry in N, it still changes an entry in M. This was not the behavior I was expecting (ie, I was expecting new to allocate a really new object). This does not occur with the mutableMatrix constructor.

For instance:

i1 : M = mutableMatrix{{1,2},{3,4}}

o1 = | 1 2 |
     | 3 4 |

o1 : MutableMatrix

i2 : N = new MutableMatrix from M

o2 = | 1 2 |
     | 3 4 |

o2 : MutableMatrix

i3 : N_(0,0) = 7

o3 = 7

i4 : N 

o4 = | 7 2 |
     | 3 4 |

o4 : MutableMatrix

i5 : M

o5 = | 7 2 |
     | 3 4 |

o5 : MutableMatrix

However, if I use the mutableMatrix constructor, this doesn't occur.

i1 : M = mutableMatrix{{1,2},{3,4}}

o1 = | 1 2 |
     | 3 4 |

o1 : MutableMatrix

i2 : N = mutableMatrix M

o2 = | 1 2 |
     | 3 4 |

o2 : MutableMatrix

i3 : N_(0,0) = 7

o3 = 7

i4 : N

o4 = | 7 2 |
     | 3 4 |

o4 : MutableMatrix

i5 : M

o5 = | 1 2 |
     | 3 4 |

o5 : MutableMatrix