[SciPy-dev] mlabwrap high-level user interface

Alexander Schmolck a.schmolck@gmx....
Mon Apr 30 08:02:35 CDT 2007

[moving this to scipy-dev]

"Brian Hawthorne" <brian.lee.hawthorne@gmail.com> writes:

> Ah, forgot one critical use case, the function call!
>>>> res = engine.svd(X, nout=1)
>>>> res = engine["svd"](X, nout=1)

As I mentioned in the other poist, I don't like that. There ought to be one
way to do things, and the first type of call is clearly what we'd like
function calls to typically look like.

I suspect that ``engine["svd"]`` ought to be equivalent to ``engine.svd()``.
The reason why I'd at least strongly consider this funny looking behavior that
is that nullary-function call vs. variable lookup is below the interface level
in matlab (i.e. syntactically undistinguishable and hence something that one
is often at liberty to change for a variable that isn't intended for mutation;
a bit like property access can be transparently replaced by a function call in
python (using e.g __getattr__) but not in lesser languages like java or C++).

> This would fall under the exact same code as the raw get below (here
> returning a function proxy). Oh, and one more suggestion, if we're going to
> treat the engine as a dict (which it is), it might also be nice to have a
> keys method to return all the names in the matlab namespace:
>>>> mlab_vars = engine.keys()  # or "vars" or "names", whatever

I'm against conflating matlab and MLabWrap-instance method namespaces,
especially since I don't see a very compelling use-case for a ``.keys``

> Though i guess if matlab already has a command for that, you could just use
> that ;) 

Indeed and if there isn't you might have a hard time implementing it anyway ;)

> One nice thing about this design is that the engine object has no
> statically defined public methods, so you don't have to worry so much about
> a method name conflicting with a matlab name.

Yes, I think we really want to avoid that.

> I think it's fine to define a private RawEngine class under the hood which
> implements open, close, get, set, and eval. Then the main user-facing engine
> will just have a reference to it and delegate to it.

Hmm, sorry I'm not 100% sure what you're proposing here -- would RawEngine
essentially be like mlabraw, but ctypes based with a class interface? If so,
yes that would indeed be the approach I'd advocate for the ctypes mlabraw
replacement (the only reason that the C++ code doesn't work like this is that
in the case of mlabraw.cpp the effort involved would IMO not have justified
the reward). IIRC, David's ctypes code already looks like this.


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