[BUG] WeightedContainer: can't iterate while I iterate

[Suor]

local cont = WeightedContainer();
cont.add("a", 10);
cont.add("b", 20);
cont.add("c", 30);
cont.add("d", 40);

foreach (k, v in cont) {
    print(k + " " + v + "\n")
    foreach (k2, v2 in cont) {
        print("inner " + k2 + " " + v2 + "\n")
    }
}

Result:

a 10
inner a 10
inner c 30
inner b 20
inner d 40

AN ERROR HAS OCCURRED [arith op + on between 'null' and 'integer']

[TaroEld]

Yeah I see. This should work:

IStack = [];
...
		if (_prev == null)
		{
			if (this.IItems == null) 
				this.IItems = ::MSU.Table.keys(this.Table);
			this.IStack.push(0)
		}
		_prev = this.IStack.top();
		this.IStack[this.IStack.len() - 1]++;

		if (_prev == this.Table.len())
		{
			this.IStack.pop();
			if (this.IStack.len() == 0)
				this.IItems = null;
			return null;
		}

		return this.IItems[_prev];

[Suor]

It will for nested case, it won't for arbitrary intermixed one. Say I create two generators:

function iter(cont) {
    foreach (k, v in cont) {
        print(k + " " + v + "\n")
        yield [k v]
    }
}

local it1 = iter(cont), it2 = iter(cont);

resume it1;
resume it1;
resume it2;
resume it2;
resume it1; // it2 not finished
resume it2; // bork

[Suor]

I think you just need a keyToIndex table to iterate and it could be shared across all generators. The behavior if container changes while iterating still might be undefined, which is fine as long as it not crashes, like original tables.

[LordMidas]

Nested iteration on squirrel classes with custom _nexti should never be used because if you "break" from the inner loop there is no way for the class to detect that. So, I'd not try to "fix" this - instead people should just not do nested iteration on these classes.

I am a proponent of the idea that the class should get a .toIterator function that will give you a standard array/table to iterate on. E.g. for the weighted container it could be:

function toIterator()
{
   return this.Table;
}

[Suor]

I would certainly call it iter() ), and this ._nexti() design is unfortunate.