fix removeU; add test

[starius]

Previous implementation used to throw the following error:

  binaryheap.lua:99 attempt to compare nil with number

[Tieske]

Thanks for the fix.

I don't know whether I like the metatable... It does not resolve the name collision, as inserting a value by a key named after a method, the key will shadow the one in the metatable, so it becomes inaccessible. Also by adding the metatable, there are 2 table lookups to find a method, first on the heap table, second on the metatable.

[starius]

Agree, current code state does not solve the problem of method names collision.

I think, the problem with name collisions can be solved by splitting the table into several tables:

1. head itself (array)
2. payloads (array)
3. map from payload to index in head
4. metatable (for methods)
5. object, in which first 3 tables are fields and metatable is metatable

2 and 3 are optional (only if payloads are used, i.e. in unique heap). 5 can be eliminated using upvalues instead of fields of a table.

I think, storing each element of a head as a table with fields "value" and "payload" is not as efficient, as two arrays are.

Side note: current implementation requires payloads not to collide with values, because all of them are stored in one table.

[Tieske]

For now, I included the fix, but left the remainder as is. Also just addd a bunch of tests. So I'm confident it works as it should now.

[Tieske]

Side note: current implementation requires payloads not to collide with values, because all of them are stored in one table.

That is not correct, the keys used are array index, and by payload, not by value.

I think, storing each element of a head as a table with fields "value" and "payload" is not as efficient, as two arrays are.

You're probably right. On the wishlist... #2

[starius]

Side note: current implementation requires payloads not to collide with values, because all of them are stored in one table.

That is not correct, the keys used are array index, and by payload, not by value.

You are right, values do not collide with payloads, but array indices do. So, numbers can't be used as payloads, as a consequence. I hope this limitation can be removed by #2

[Tieske]

done!