This has been a point of confusion and terminology mismatch for me too when reading this discussion. Rather than debate about it, lets look at the code, how about we submit the same small GUI program in each of the toolkits, it should be immediatly obvious how 'high' or 'low' level they are by whatever standards you wish to apply. I propose a simple program which pops up a window saying 'Hello World' with a button saying 'Bye' which you click and it changes the message to 'Goodbye'. if you click the button again the program exits. this should (hopefully) be a short program with most toolkits and demonstrate how one lays out 2 widgets, and responds to user input and mutates the display. note, this is not to compare the toolkits themselves, but the haskell APIs used to access them. I'd like to see samples using gtk+hs gtk2hs Ports GIO (on top of Ports) ObjectIO FranTk Fruit Htk ... more? actually, putting links to these little demo programs on the haskell library page would probably be tons more useful than the current information. John On Thu, Jan 30, 2003 at 11:36:24PM +0100, Daan Leijen wrote:
Hi Wolfgang,
several GUI-related e-mails of the last days spoke about different library "levels" (high, medium, low). I'm not sure, which the term "level" refers to. Does it refer to (a) different programming paradigms (high: functional; low: imperative) or (b) different views onto GUIs (high: application types (MDI, SDI etc.), common dialogs etc.; low: just widgets or even drawing primitives etc.)?
I can't speak for others but I interpreted the 'level' as the Haskell programmers level. That is, 'high level' means something really declarative like franTk or Fudgets. 'medium level' means that the library is imperative but offers a lot of convenient functionality, like TkGofer. Low-level means that it is imperative and offers no convenience, as Win32 or basic gtk2hs.
My opinion concerning (L) is the following: If (a) is meant, (L) should be low-level and be implemented in C with a thin Haskell layer on top of it. (The C interface would also be useable outside the Haskell context.) If (b) is meant, (L) should be as high-level as it must be to provide native look-and-feel.
In my opinion, (L) should be "low-level" from a Haskell programmer perspective. That is, there should be medium level library (A) built on top of (L) that offers convenient functions to access (L). In this sense, we could probably better talk about a core-functionality library for the medium level library (A). I think that it is really important to make this distinction, as we can share the work on (A) and make it much easier to make a port of (L).
However, at the same time, (L) should be "high-level" from a GUI perspective to be as portable as possible and to give a native look-and-feel. (i.e. your (b) option). As you say, it should talk in terms of application types and common dialogs but not just in terms of drawing primitives.
Port tries to be these things, but we (me and Axel) are still discussing whether Port is actually "high level" enough from a GUI perspective or wheter we need to look for another kind of interface.
A related question: What do you mean with "abstraction"? Has it something to do with "high-level" in the (b) meaning?
This depends entirely on the context :-) I think I used "abstraction" in connection with the (A) layer. In that sense, I meant that the (A) library should offer convenient abstractions that the (L) layer doesn't offer. For example, we can abstract over resource allocation by using foreign pointers on Bitmap resources. Or use type classes to be able to close any widget with "close" instead of "closeDialog" or "closeWindow".
All the best, Daan.
for an example of how I see the distinction between (A) and (L), you could browse the online docs of GIO (A) and Port (L) at: http://htoolkit.sourceforge.net
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