AMatrix constructor Null safety

1. jrpn
2. jrpn15.matrix
3. AMatrix
4. AMatrix constructor

AMatrix class

1. Constructors
2. AMatrix
3. Properties
4. columns
5. hashCode
6. rows
7. runtimeType
8. toStringDim
9. Methods
10. dot
11. equivalent
12. formatValueWith
13. get
14. getF
15. identity
16. noSuchMethod
17. residual
18. set
19. setF
20. toString
21. visit
22. Operators
23. operator ==