Re: [Haskell-cafe] I miss OO

On Thu, Nov 26, 2009 at 12:03 AM, Eugene Kirpichov wrote:

Hi,

Are you sure you need to store the time *inside* your "objects" instead of using, say, pairs "(Time, YourObject)" (and lists of them instead of lists of your objects)? It would seem strange to me that a note HAS-A time even in an OO design: more likely, a note is associated with a time, and this is modeled by pairing them.

+1 This hadn't occurred to me, but in retrospect is quite obvious. In FRP notation, these are "Futures", eg. Future Note. Luke

2009/11/25 Michael Mossey :

...

I'm fairly new to Haskell, and starting to write some big projects. Previously I used OO exclusively, mostly Python. I really miss the "namespace" capabilities... a class can have a lot of generic method names which may be identical for several different classes because there is no ambiguity.

In my musical application, many "objects" (or in Haskell, data) have a time associated with them. In Python I would have an accessor function called "time" in every class.

So if I have objects/data note1, cursor1, and staff1,

Python:  note1.time()  cursor1.time()  staff1.time()

Haskell needs something like  note_time note1  cursor_time cursor1  staff_time staff1

which is a lot more visually disorganized.

What's worse, I have a moderate case of RSI (repetitive strain injury) so I type slowly and depend on abbreviations a lot. I use the souped-up abbreviation capabilities of Emacs. Let's say I have a field/member-variable called orientedPcSet that is used across many classes. In Python, I can create an abbreviation for that and it is useful many times. In Haskell, I might need

someType_orientedPcSet someOtherType_orientedPcSet thirdType_orientedPcSet

which prevents me from using abbreviations effectively (especially the dynamic-completion feature). (It would help to make the underscore not part of word syntax, but that's not ideal.)

So I'm thinking of moving to a scheme in Haskell using modules, most types being defined in their own modules, and doing qualified imports. Generic names like 'time' can be defined in each module w/o clashing. Then I have

Note.time note1 Cursor.time cursor1 Staff.time staff1

This is very useful because I can define abbreviations for the type name and for oft-used accessor function names and these abbrevs are more organized, easier to remember, and easier to combine.

I would be interested in comments... is this a good way to do things? Am I trying too hard to impose OO on Haskell and is there a better way?

Thanks, Mike

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-- Eugene Kirpichov Web IR developer, market.yandex.ru _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe