• Paul D. Anderson (7/7) Apr 24 2009 Looking at Don Clugston's BigInt code I see usage of "*this":
• Don (10/22) Apr 24 2009 It's passing by value, since BigInt is a struct, not a class. 'this' is
• Paul D. Anderson (3/28) Apr 24 2009 Thanks, Don.

Paul D. Anderson <paul.d.removethis.anderson comcast.andthis.net> writes:

Looking at Don Clugston's BigInt code I see usage of "*this":

BigInt opMulAssign(T: BigInt)(T y) {
       *this = mulInternal(*this, y);
         return *this;
     }

I think I know what it does (passes this by reference) but I can't find any
documentation that explains the usage. Can anyone point me to a source??

Paul

Don <nospam nospam.com> writes:

Paul D. Anderson wrote:
 Looking at Don Clugston's BigInt code I see usage of "*this":
 
 BigInt opMulAssign(T: BigInt)(T y) {
        *this = mulInternal(*this, y);
          return *this;
      }
 
 I think I know what it does (passes this by reference) but I can't find any
documentation that explains the usage. Can anyone point me to a source??
 
 Paul
 
 

It's passing by value, since BigInt is a struct, not a class. 'this' is 
a pointer to the struct, so *this is the struct itself. In the case of 
BigInt, the struct only contains an bool and a dynamic array, for a 
total of 10 bytes or so, so it's not much bigger than a pointer.

I believe the behaviour of 'this' in structs changed recently (but 
probably only in D2?) The BigInt wrapper class would be a bit different 
in D2.

BTW BigInt uses structs, not classes, and part of the reason for this is 
that you _cannot_ have value semantics with a class.

Paul D. Anderson <paul.d.removethis.anderson comcast.andthis.net> writes:

Don Wrote:

 Paul D. Anderson wrote:
 Looking at Don Clugston's BigInt code I see usage of "*this":
 
 BigInt opMulAssign(T: BigInt)(T y) {
        *this = mulInternal(*this, y);
          return *this;
      }
 
 I think I know what it does (passes this by reference) but I can't find any
documentation that explains the usage. Can anyone point me to a source??
 
 Paul
 
 

 It's passing by value, since BigInt is a struct, not a class. 'this' is 
 a pointer to the struct, so *this is the struct itself. In the case of 
 BigInt, the struct only contains an bool and a dynamic array, for a 
 total of 10 bytes or so, so it's not much bigger than a pointer.
 
 I believe the behaviour of 'this' in structs changed recently (but 
 probably only in D2?) The BigInt wrapper class would be a bit different 
 in D2.
 
 BTW BigInt uses structs, not classes, and part of the reason for this is 
 that you _cannot_ have value semantics with a class.
 

Thanks, Don.

Paul