Differentiation of operations regarding operands' preservation

[neithernut]

I just relized that we have to differentiate whether an operation should preserve the previous operands or not.
Always preserving the operands of an operation has a huge performance impact, which we did not consider when defining the interface. (We're speaking O(log(n)) vs. O(n) for merges)
If we'd write the lib in C++, we would simply create overloads using move-semantics to differentiate both cases, but as the lib will be C-code, we should discuss how to represent non-preservative versions of the operations in our interface (e.g. as additional functions).

[matthiasbeyer]

We could simply add more functions, having a _np postfix.

If I understand things right, we will add functions which allocate new objects instead of altering old ones, right?

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From my understanding, this has only to be implemented for some functions:

• r_set_union()
• r_set_intersection()
• r_set_xor()
• r_set_select()
• r_set_exclude()

And it also relates to the AVL implementation, as the AVL Tree needs features which allow to revert such changes.

But, after reviewing the code again:

r_set_union() Takes three arguments: A destination, a first source and a second one. So we basically already have this behaviour, as if we pass three different sets, we can revert the 'union' change simply by removing the destination set. The same goes for the other mentioned functions.

Or am I misunderstanding something?

[matthiasbeyer]

Relates to #12

[neithernut]

The second operand will currently be unaffected in every case. For unios this may result in copying ever single item in that operand, which may be unneccessary.
Thus, we should have functions which destroy/consume the second operand.

[matthiasbeyer]

👍

How to?

[neithernut]

Same function, but with the last set-parameter being non-const and with some suffix ("_nc" for "Non Const")?

[matthiasbeyer]

Maybe "_d" for "destructive"?

[neithernut]

Maybe.
Or "_c" for "consuming"?

[TheNeikos]

👍 for consuming

[matthiasbeyer]

👍