3 ms·

So copy-on-write basically?

• hgsgm 4y ago
  No, there is no "write" because the old value never chnages. It's "create an overlay on write"
  • deleted 4y ago
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• arc-in-space 4y ago
  Copy-on-write generally refers to copying everything on every write; this is a persistent data structure, which can do updates while only copying a small part of itself. Same purpose as COW, but more efficient for larger data structures we want to make lots of small updates on.
• Joker_vD 4y ago
  Well, yeah, only there ain't any writes (and therefore, no copying). The simplest example would be with linked lists, I suppose: you have a list A->B->C, then you take the B->C sublist and prepend X to it, so you now have X->B->C, but A->B->C is still around, and "B->C" part is shared between those.
• herbstein 4y ago
  Yes, but with granularity at the "node" level instead of being across the whole container. Imagine a linked list. If you add prepend an element to an existing list, no copy is necessary. It's just a new head with the tail being the original list. That's an easy case. If you add a node in the middle of the list you can still share the unchanged tail between the two slightly different prefix sequences.
• rkangel 4y ago
  No, because you don't copy the whole structure. You create a new partial structure. E.g. let's say you create a map with keys A and B. You then insert a new key C. In memory you might have two objects: One is the origi al map with A and B and the other has "Key C and a ref to the first map".