Minimal constructors

[johnmyleswhite]

Why discussing the recent changes to DA constructors, @simonster made a suggestion that I really like that would have us remove a constructor that isn't strictly.

I'd like to propose the following design principle:

• We only offer two constructors for DA's and PDA's:
  • Construction using the implementation details
  • Construction using an empty DA/PDA of a specific type and size.
• For creating objects, one either uses:
  • Literals written using @data or @pdata
  • Explicit conversions.

Does this sound right to you, @simonster?

[nalimilan]

Not sure how I feel about this. Being able to create a DataArray from an array using the short DataArray(a) rather than the cumbersome convert(DataArray, a) is nice, just like there is sparse(a).

Anyway I don't care about other fancy constructors.

[johnmyleswhite]

Let's just add data and pdata functions for that use case.

[simonster]

Sounds good to me. It would also be good if @data([a]) did conversion to a DataArray, as it does conversion to an Array in Base (but see JuliaLang/julia#3737). I'll see if I can make that happen.

[johnmyleswhite]

Shouldn't be too hard, just special case the macros to rewrite calls to the new data and pdata functions instead of calling the constructors.

[johnmyleswhite]

I added data and pdata in ae7d8203a1089b2cf05494c6cc209a6043f51b86

[nalimilan]

Good!