default '==' on structs

[Lars T. Kyllingstad]

On Wed, 02 Feb 2011 15:55:53 +0100, spir wrote:

> Hello,
> 
> What are the default semantics for '==' on structs?
> 
> I ask this because I was forced to write opEquals on a struct to get
> expected behaviour. This struct is basically:
> 
> struct Lexeme {
>      string tag;
>      string slice;
>      Ordinal index;
> }
> 
> Equal Lexeme's compare unequal using default '=='. When I add:
> 
>      const bool opEquals (ref const(Lexeme) l) {
>          return (
>                 this.tag   == l.tag
>              && this.slice == l.slice
>              && this.index == l.index
>          );
>      }
> 
> then all works fine. What do I miss?

I think the compiler does a bitwise comparison in this case, meaning that 
it compares the arrays' pointers instead of their data.  Related bug 
report:

  http://d.puremagic.com/issues/show_bug.cgi?id=3433

-Lars