MAT statements and user defined types

[Michael Bell]

I've just discovered that MAT statements don't work with arrays within user defined types.

For example, given a UDT

 
TYPE Population
  State(1 to 3) as EXT
  Transition(1 to 3,1 to 3) as EXT
END TYPE

And

 
LOCAL P as Population

I can access P.State() and P.Transition() as arrays in the normal way, but I can't do assignments such as

 
MAT P.State()=AnotherVector()
MAT P.State()=ZER
MAT P.Transition()=IDN

These result in compile time error 526: Period not allowed. Of course it's not a big deal to do matrix operations the long way round, but it would be good to have the convenience of MAT statements with UDTs sometimes. A New Feature Suggestion has been lodged with those nice people at [email protected]...

[Michael Mattias]

I've just discovered that MAT statements don't work with arrays within user defined types

No "ARRAY" statements work with "Arrays within types".

"Arrays within types" are not "Arrays" [cap A] as used elsewhere in the documentation.

"Arrays within types" are in fact "arrays" [small A], but that's too easily confused with "Arrays" [caps again] so I just call them "tables." [case not signficant]

MCM

[Eric Pearson]

Would DIM...AT provide a workaround here?

DIM an array AT the memory location of the UDT's pseudo-array, and use the MAT statement on the "overlay" array?

-- Eric

[Michael Bell]

Michael M: I take your point. Still, as a minor convenience, I'd like to be able to do the same things to arrays as Arrays. Not of huge importance, but something I'd use if it was available.

Eric: Thanks - out of interest I tried it (DIM V() AS EXT AT VARPTR(P.State()), then MAT operations on V()). Didn't seem to work, but I could easily have done it wrong as that's the first time I'd even heard of DIM AT. In practice I'd just do the assignment long-hand.

[Michael Mattias]

out of interest I tried it (DIM V() AS EXT AT VARPTR(P.State()), then MAT operations on V()). Didn't seem to work,

That should not even compile.

REDIM V(2  [ or "1 to 3"] ) AS EXT AS VARPTR(p.State(1))

... should both compile and work.

MCM

[Michael Bell]

Yes - that works, thanks! I mistyped my original effort in my last post, but I still missed that varptr should be to P.State(1) rather than P.State().

So...

  DIM V(1 TO 3) AS EXT AT VARPTR(P.State(1))
  MAT V()=V2()

works exactly as if I had done the MAT statement on P.State() directly.

Lots to learn...