Exercise at end of Ch. 56 of "Programming in D"

johntp albertqaeda at yahoo.com
Mon Aug 15 03:19:43 UTC 2022

On Monday, 15 August 2022 at 02:23:34 UTC, Ali Çehreli wrote:
> Wow! Are people actually working on those? :)

Absolutely.  Thanks for the book.  I'm enjoying it.

> At first, I couldn't even get the code to compile due to 
> const-correctness issues with opCmp. :/ I used the following 
> cast():
>   foreach (i, point; points) {
>       immutable comparison = (cast()point).opCmp(rhs.points[i]);
>       // ...
>   }

For some reason I didn't have this problem.

> The bug was with trying to implement that unnatural "ignore the 
> color" in the comparison logic but then toHash was taking 
> advantage of existing array hashing code, which had no idea of 
> the programmer's requirement:

I thought that was the problem, but wasn't sure.  I wasn't 
getting the same hash code for area1 and area2.

Your solution worked. I guess it is a little unnatural to ignore 
the color.  I tried overriding the toHash() of Point, but I don't 
know enough D to get it to work.  I wonder if that could be a 

Thanks so much for the reply.

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