• H. S. Teoh (18/18) Apr 16 2020 Just out of curiosity, is there a mixin template or something like that
• Steven Schveighoffer (6/24) Apr 16 2020 This used to work:
• H. S. Teoh (6/17) Apr 16 2020 Ooh, very nice! Why didn't I think of that. ;-) Thanks!
• Steven Schveighoffer (5/20) Apr 16 2020 Hehe, we all didn't think of that. I remember asking the same question I...

"H. S. Teoh" <hsteoh quickfur.ath.cx> writes:

Just out of curiosity, is there a mixin template or something like that
in Phobos for implementing a default .opEquals that does member-wise
comparison of a class object? Something like this:

	mixin template DefaultOpEquals(T) {
		bool opEquals(Object o) {
			auto t = cast(T) o;
			if (t is null) return false;
			foreach (field; __traits(getAllMembers, T)) {
				if (this.field != t.field) return false;
			}
			return true;
		}
	}

It's annoying to have to write an .opEquals method for every class that
basically just does the same thing.


T

-- 
Verbing weirds language. -- Calvin (& Hobbes)

Steven Schveighoffer <schveiguy gmail.com> writes:

On 4/16/20 1:21 PM, H. S. Teoh wrote:
 Just out of curiosity, is there a mixin template or something like that
 in Phobos for implementing a default .opEquals that does member-wise
 comparison of a class object? Something like this:
 
 	mixin template DefaultOpEquals(T) {
 		bool opEquals(Object o) {
 			auto t = cast(T) o;
 			if (t is null) return false;
 			foreach (field; __traits(getAllMembers, T)) {
 				if (this.field != t.field) return false;
 			}
 			return true;
 		}
 	}
 
 It's annoying to have to write an .opEquals method for every class that
 basically just does the same thing.
 

This used to work:

this.tupleof == t.tupleof;

But you may have to use std.traits or something to get in all the base 
class fields.

-Steve

"H. S. Teoh" <hsteoh quickfur.ath.cx> writes:

On Thu, Apr 16, 2020 at 01:32:45PM -0400, Steven Schveighoffer via
Digitalmars-d wrote:
 On 4/16/20 1:21 PM, H. S. Teoh wrote:
 Just out of curiosity, is there a mixin template or something like
 that in Phobos for implementing a default .opEquals that does
 member-wise comparison of a class object? Something like this:


[...]
 It's annoying to have to write an .opEquals method for every class
 that basically just does the same thing.
 

 
 This used to work:
 
 this.tupleof == t.tupleof;

Ooh, very nice!  Why didn't I think of that. ;-)  Thanks!


T

-- 
Don't throw out the baby with the bathwater. Use your hands...

Steven Schveighoffer <schveiguy gmail.com> writes:

On 4/16/20 1:51 PM, H. S. Teoh wrote:
 On Thu, Apr 16, 2020 at 01:32:45PM -0400, Steven Schveighoffer via
Digitalmars-d wrote:
 On 4/16/20 1:21 PM, H. S. Teoh wrote:
 Just out of curiosity, is there a mixin template or something like
 that in Phobos for implementing a default .opEquals that does
 member-wise comparison of a class object? Something like this:


 [...]
 It's annoying to have to write an .opEquals method for every class
 that basically just does the same thing.

 This used to work:

 this.tupleof == t.tupleof;

 
 Ooh, very nice!  Why didn't I think of that. ;-)  Thanks!

Hehe, we all didn't think of that. I remember asking the same question I 
don't know how many years ago, and someone told me that answer.

It's probably somewhere in these forums...

-Steve