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digitalmars.D.learn - opApply and attributes

reply solidstate1991 <laszloszeremi outlook.com> writes:
See implementation of data structure here: 
https://github.com/ZILtoid1991/collections-d/blob/master/source/collections/treemap.d#L565

If I try to compile this code, it'll fail, limiting it's usecase:

 safe pure unittest {
	alias IntMap = TreeMap!(int, int, false);
	IntMap test;
	test[5] = 5;
	test[7] = 7;
	test[3] = 3;
	foreach(elem, key; test) {
		assert(elem == key);
	}
}

I know that implementing foreach with other means do exist, and I 
used them in my other data structures, but it's much more 
difficult (and potentially slower) to implement that within a 
binary search tree.

Should I change the `opApply` into the `popfront` - `front` - 
`empty` trinity, or write a template that overrides all the 
potential attribute combinations?

Maybe D needs a template for attributes somehow, or something 
like that.
Jul 06 2020
next sibling parent reply Paul Backus <snarwin gmail.com> writes:
On Tuesday, 7 July 2020 at 00:20:40 UTC, solidstate1991 wrote:

 See implementation of data structure here: 
 https://github.com/ZILtoid1991/collections-d/blob/master/source/collections/treemap.d#L565

 If I try to compile this code, it'll fail, limiting it's 
 usecase:

  safe pure unittest {
 	alias IntMap = TreeMap!(int, int, false);
 	IntMap test;
 	test[5] = 5;
 	test[7] = 7;
 	test[3] = 3;
 	foreach(elem, key; test) {
 		assert(elem == key);
 	}
 }


You can make opApply a template:

     int opApply(Dg)(Dg dg)
         if (is(Dg : scope int delegate(ref E)))
     {
         // etc.
     }

Because `scope int delegate(ref E)  safe` implicitly converts to 
`scope int delegate(ref E)`, this version will accept both  safe 
and non- safe delegates. (And likewise for the other function 
attributes.)
Jul 07 2020
next sibling parent Stanislav Blinov <stanislav.blinov gmail.com> writes:
On Tuesday, 7 July 2020 at 13:33:41 UTC, Paul Backus wrote:


 You can make opApply a template:

     int opApply(Dg)(Dg dg)
         if (is(Dg : scope int delegate(ref E)))
     {
         // etc.
     }

 Because `scope int delegate(ref E)  safe` implicitly converts 
 to `scope int delegate(ref E)`, this version will accept both 
  safe and non- safe delegates. (And likewise for the other 
 function attributes.)


Yeah, but unfortunately then this won't work:


 	foreach(elem; test) {
 		assert(elem == key);
 	}


you'd have to spell out the types for `elem`.
Jul 07 2020
prev sibling parent solidstate1991 <laszloszeremi outlook.com> writes:
On Tuesday, 7 July 2020 at 13:33:41 UTC, Paul Backus wrote:

 You can make opApply a template:

     int opApply(Dg)(Dg dg)
         if (is(Dg : scope int delegate(ref E)))
     {
         // etc.
     }

 Because `scope int delegate(ref E)  safe` implicitly converts 
 to `scope int delegate(ref E)`, this version will accept both 
  safe and non- safe delegates. (And likewise for the other 
 function attributes.)


Unfortunately this doesn't really work, even with explicitly 
defined foreach arguments.
Jul 07 2020
prev sibling parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 7/6/20 5:20 PM, solidstate1991 wrote:> See implementation of data 
structure here:

 


https://github.com/ZILtoid1991/collections-d/blob/master/source/collec
ions/treemap.d#L565 


 If I try to compile this code, it'll fail, limiting it's usecase:

  safe pure unittest {
      alias IntMap = TreeMap!(int, int, false);
      IntMap test;
      test[5] = 5;
      test[7] = 7;
      test[3] = 3;
      foreach(elem, key; test) {
          assert(elem == key);
      }
 }


I am not sure whether I understand it correctly but there has been a 
request for opApply() to gain the attributes of the delegate (or the 
range?). In other words, "transfer the attributes to opApply". This is 
needed because I want opApply() to work with any foreach body, 
attributes of which opApply() cannot know.

I am sure I created an issue on Dlang bug tracker for Weka on this topic 
but I can't find it now. (Aside: The search boxes on the bug tracker are 
inferior to the automatic search feature that works when creating a 
bug.) Anyway, this one seems related:

   https://issues.dlang.org/show_bug.cgi?id=7543

Ali
Jul 07 2020
parent reply solidstate1991 <laszloszeremi outlook.com> writes:
On Tuesday, 7 July 2020 at 20:53:05 UTC, Ali Çehreli wrote:

 I am not sure whether I understand it correctly but there has 
 been a request for opApply() to gain the attributes of the 
 delegate (or the range?). In other words, "transfer the 
 attributes to opApply". This is needed because I want opApply() 
 to work with any foreach body, attributes of which opApply() 
 cannot know.

 I am sure I created an issue on Dlang bug tracker for Weka on 
 this topic but I can't find it now. (Aside: The search boxes on 
 the bug tracker are inferior to the automatic search feature 
 that works when creating a bug.) Anyway, this one seems related:

   https://issues.dlang.org/show_bug.cgi?id=7543

 Ali


Something like that, but with  safe, pure, etc. attributes.
Jul 13 2020
parent solidstate1991 <laszloszeremi outlook.com> writes:
On Tuesday, 14 July 2020 at 00:17:14 UTC, solidstate1991 wrote:

 Something like that, but with  safe, pure, etc. attributes.


I've tried to "bruteforce" it by generating functions with 
combinations of attributes, and it kinda works, but is a very 
janky solution.

I'll brainstorm some DIP to fix this issue.
Jul 16 2020