presenter::mkExpand

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Martin Meyer
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presenter::mkExpand

Unread post by Martin Meyer » 26 Jun 2019 0:25

Hello Thomas,

when setting a breakpoint in below code at the indicated line and running it in the debugger (in build 902), a line for variable Num is displayed in the "Variables in the Current Clause" window. However (with "Native View" not checked on) the line cannot be expanded by mouse click. I suppose that is not intended?

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domains     num = unsigned [presenter(present_num)].   class predicates     getNumName : (num) -> string. clauses     getNumName(0) = "zero" :-         !.     getNumName(1) = "one" :-         !.     getNumName(_) = "many".   class predicates     present_num : presenter::presenter{num}. clauses     present_num(Num) = present_num(Num, Num).   class predicates     present_num : (num Num, unsigned NumUnsigned) -> presenter::presentation. clauses     present_num(Num, NumUnsigned) = presenter::mkExpand(Name, NumUnsigned) :-         Name = getNumName(Num).   class predicates     test : (num). clauses     test(Num) :-         stdIO::write(Num).  %set a breakpoint here   clauses     run() :-         test(1).
Regards Martin

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Thomas Linder Puls
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Re: presenter::mkExpand

Unread post by Thomas Linder Puls » 26 Jun 2019 11:25

No, that is a bug.

By the way, (it will not solve the bug, but) you can write your presenter like this:

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class predicates     present_num : presenter::presenter{num}. clauses     present_num(Num) = presenter::mkExpand(getNumName(Num), hasDomain(unsigned, Num)).
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Thomas Linder Puls
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Re: presenter::mkExpand

Unread post by Thomas Linder Puls » 27 Jun 2019 13:33

I am sorry I was confused when I answered before. An "expand" presentation will be presented as its first argument, and expand as the second term. But an unsigned doesn't expand, so this presentation will not expand.

In your case you should use a fixed presentation with a string and a "child only" component:

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class predicates     present_num : presenter::presenter{num}. clauses     present_num(Num) =         presenter::mkPresenter_fixed(             presenter::fp_string(getNumName(Num)),             presenter::mkFP_childOnly_term("Value", hasDomain(unsigned, Num))).
Which will give this
num_presenter.png
num_presenter.png (5.25 KiB) Viewed 612 times
Regards Thomas Linder Puls
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Martin Meyer
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Re: presenter::mkExpand

Unread post by Martin Meyer » 27 Jun 2019 17:03

Ahhh :shock: OK, I got it. And reading the wiki more carefully I see that is also documented well. Thank you!
Regards Martin

Martin Meyer
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Re: presenter::mkExpand

Unread post by Martin Meyer » 30 Jun 2019 9:26

But why does below wrapper object not expand (in non-native view)?

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interface obj     [presenter] end interface obj   class obj : obj end class obj   implement obj     open presenter   clauses     presenter() = mkPresenter_fixed(         fp_string("I am an obj"),         presenter::mkFP_childOnly_term("I am the expansion of an obj", compiler_version)).   end implement obj   %===   interface wrapper     [presenter] end interface wrapper   class wrapper : wrapper   constructors     new : (obj).   end class wrapper   implement wrapper     open presenter   facts     obj : obj.   clauses     new(Obj) :-         obj := Obj.   clauses     presenter() = mkExpand("I am a wrapper", obj).   end implement wrapper   %===   implement main   clauses     run() :-         Obj = obj::new(),         Wrapper = wrapper::new(Obj),         stdIO::write(Wrapper, ", ", Obj).  %set a breakpoint here   end implement main
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Thomas Linder Puls
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Re: presenter::mkExpand

Unread post by Thomas Linder Puls » 1 Jul 2019 10:15

Yes, that it is a good question :-). We will look at it.
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Thomas Linder Puls
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Re: presenter::mkExpand

Unread post by Thomas Linder Puls » 1 Jul 2019 11:52

My brain has looked into some forgotten memory slots (or invented a story).

Though this is not what consistent with the documentation, I think this is deliberate. What happens is that a an "expand" presentation, will show/write the first argument, but expand like the native expansion of the second argument.

The reason for using the native expansion of the second argument is exactly the object case, where you want a nice string-presentation, but a straight forward expansion with all the facts, etc.
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Thomas Linder Puls
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Re: presenter::mkExpand

Unread post by Thomas Linder Puls » 1 Jul 2019 13:45

My colleagues agree it is the native expansion that is used. I have added the word to the documentation.
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Martin Meyer
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Re: presenter::mkExpand

Unread post by Martin Meyer » 1 Jul 2019 22:45

Yes, it's all consistent now. Thank you.
Regards Martin

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