• FoxyBrown (5/5) Jul 21 2017 Is there a way to easily find the differences between to struct
• Era Scarecrow (8/13) Jul 21 2017 This is entirely dependent on the structs in question, you can't
• FoxyBrown (5/21) Jul 21 2017 No, it isn't. It is a concept, wasn't mean to be taken as literal
• Nicholas Wilson (21/44) Jul 21 2017 use opCmp in conjunction with __traits(allMembers,T)
• FoxyBrown (2/24) Jul 21 2017 thanks, I'll try it out.

FoxyBrown <Foxy Brown.IPT> writes:

Is there a way to easily find the differences between to struct 
instances? I would like to report only the differences

e.g.,

writeln(s1 - s2);

prints only what is different between s1 and s2.

Era Scarecrow <rtcvb32 yahoo.com> writes:

On Friday, 21 July 2017 at 21:03:22 UTC, FoxyBrown wrote:
 Is there a way to easily find the differences between to struct 
 instances? I would like to report only the differences

 e.g.,

 writeln(s1 - s2);

 prints only what is different between s1 and s2.

  This is entirely dependent on the structs in question, you can't 
just subtract any struct from another struct unless it knows how 
to do it.

  Depends on what the structures hold. You'll probably have to 
either make an opSub, a function to call opBinary!"-", or do 
opCmp which returns which is higher/lower (and may be as simple 
as subtraction).

FoxyBrown <Foxy Brown.IPT> writes:

On Friday, 21 July 2017 at 22:35:20 UTC, Era Scarecrow wrote:
 On Friday, 21 July 2017 at 21:03:22 UTC, FoxyBrown wrote:
 Is there a way to easily find the differences between to 
 struct instances? I would like to report only the differences

 e.g.,

 writeln(s1 - s2);

 prints only what is different between s1 and s2.


No, it isn't. It is a concept, wasn't mean to be taken as literal 
D code.

  This is entirely dependent on the structs in question, you 
 can't just subtract any struct from another struct unless it 
 knows how to do it.

  Depends on what the structures hold. You'll probably have to 
 either make an opSub, a function to call opBinary!"-", or do 
 opCmp which returns which is higher/lower (and may be as simple 
 as subtraction).

Why do I want to go through all that trouble? A simple binary 
compare should suffice.

Nicholas Wilson <iamthewilsonator hotmail.com> writes:

On Friday, 21 July 2017 at 23:38:51 UTC, FoxyBrown wrote:
 On Friday, 21 July 2017 at 22:35:20 UTC, Era Scarecrow wrote:
 On Friday, 21 July 2017 at 21:03:22 UTC, FoxyBrown wrote:
 Is there a way to easily find the differences between to 
 struct instances? I would like to report only the differences

 e.g.,

 writeln(s1 - s2);

 prints only what is different between s1 and s2.


 No, it isn't. It is a concept, wasn't mean to be taken as 
 literal D code.

  This is entirely dependent on the structs in question, you 
 can't just subtract any struct from another struct unless it 
 knows how to do it.

  Depends on what the structures hold. You'll probably have to 
 either make an opSub, a function to call opBinary!"-", or do 
 opCmp which returns which is higher/lower (and may be as 
 simple as subtraction).

 Why do I want to go through all that trouble? A simple binary 
 compare should suffice.

use opCmp in conjunction with __traits(allMembers,T)

struct Example
{
     int a,b,c;
     string d,e,f;
}

void difference(alias func, T)(T t1, T t2) if(__traits(compiles, 
func(t1,t2)))
{
     foreach(U; __traits(allMembers,T)
     {
         if (mixin("t1." ~ U.stringof~ ".opCmp(t2." ~ U.stringof 
~")")
             func(t1,t2);
     }

}

auto a =  Example(1,2,3,"foo","bar",baz");
auto a =  Example(1,2,42,"foo","bar",quux");

difference!(writeln)(a,b); // hopefully prints 343\nbazquux

Not tested but should give you an idea to adapt as needed.

FoxyBrown <Foxy Brown.IPT> writes:

On Saturday, 22 July 2017 at 01:04:48 UTC, Nicholas Wilson wrote:
 On Friday, 21 July 2017 at 23:38:51 UTC, FoxyBrown wrote:
 [...]

 use opCmp in conjunction with __traits(allMembers,T)

 struct Example
 {
     int a,b,c;
     string d,e,f;
 }

 void difference(alias func, T)(T t1, T t2) 
 if(__traits(compiles, func(t1,t2)))
 {
     foreach(U; __traits(allMembers,T)
     {
         if (mixin("t1." ~ U.stringof~ ".opCmp(t2." ~ U.stringof 
 ~")")
             func(t1,t2);
     }

 }

 auto a =  Example(1,2,3,"foo","bar",baz");
 auto a =  Example(1,2,42,"foo","bar",quux");

 difference!(writeln)(a,b); // hopefully prints 343\nbazquux

 Not tested but should give you an idea to adapt as needed.

thanks, I'll try it out.