Testing for object property supporting "<" comparison

Chris Piker chris at hoopjump.com
Tue May 11 19:42:34 UTC 2021


Hi D

I'm working on a bit of code that handles selecting one *.front 
from multiple range-ish objects.  It's a select-or-drop algorithm 
for a data streaming service, the details aren't important.

The algorithm takes a range of something I'll call 
"PriorityRange" objects.  PriorityRange objects are like input 
ranges, but have a few extra members.  The set is:

   .empty     :  Returns bool
   .front     :  Returns something non-void
   .popFront():  Return void

   .priority  :  Returns something comparable via "<" to other
                 .priority values for all input PriortyRanges

   .min       :  Returns something comparable to .max below
                 via "<" for all input PriorityRanges

   .max       :  Returns something comparable to .min above
                 via "<" for all input PriorityRanges

I noticed the isInputRange(R) enum from std/range/primitives.d 
and am wondering how to setup a similar check, call it 
"isPriorityRange(PR)".

My problem is that I don't know how to specify that properties 
must be comparable via "<".  I took a look at the Traits module, 
but there are more things that are comparable then Arithmetic or 
Floating point types.  Also, since the compiler will catch 
objects that don't have these properties, maybe an enum check is 
not worth implementing.

Thanks very much for any advice you might have,
Cheers



More information about the Digitalmars-d-learn mailing list