Associative array literal: length wrong when duplicate keys found

[Ivan Kazmenko via Digitalmars-d-learn]

On Tuesday, 31 January 2017 at 17:20:00 UTC, John Colvin wrote:
> It's a bug, please report it. The initializer should be 
> statically disallowed.
>
> Adding a .dup works around the problem.

OK.  Hmm, but the real use case was a bit more complicated, more 
like:

-----
int n = 10;
foreach (i; 0..n)
     foreach (j; 0..n)
         foreach (k; 0..n)
             ... and maybe a couple more ...
             if ([i: true, j: true, k: true].length == 3)
                 {...} // i, j, k is a set of distinct values
-----

Here, we don't know i, j and k statically, yet the problem is the 
same.

Anyway, I'll file a bug report.

> By the way, you can do sets like this, avoiding storing any 
> dummy values, only keys:
>
> struct Set(T)
> {
> 	void[0][T] data;
> 	
> 	void insert(T x)
> 	{
> 		data[x] = (void[0]).init;
> 	}
> 	
> 	void remove(T x)
> 	{
> 		data.remove(x);
> 	}
> 	
> 	bool opBinaryRight(string op : "in")(T e)
> 	{
> 		return !!(e in data);
> 	}
> 	
> 	// other things like length, etc.
> }
>
> unittest
> {
> 	Set!int s;
> 	s.insert(4);
> 	assert(4 in s);
> 	s.remove(4);
> 	assert(4 !in s);
> }

Yeah, thanks for the recipe!  I usually do bool [key] since it 
does not add much overhead, but would definitely like the real 
set (void[0] or otherwise) when performance matters.

Ivan Kazmenko.