the switch object is slow because of recursion

[maxonfjvipon]

Current implementation of switch object uses tuple.at object which is convenient for retrieval object by index but quite heavy.
Instead we can implement some recursive algorithm that can just do cases.head and cases.tail instead. Something similar to #3048 but in EO

[l3r8yJ]

@maxonfjvipon can you help a bit, did I understand correctly how this implementation works?

[cases] > switch
  cases.length > len!

  # Take case by given index.
  # If case key is true, return case value.
  # Otherwise take next case.
  [index] > case-at
    if. > @
      index.eq ^.len
      true
      if.
        at.
          ^.cases.at index > case
          0
        case.at 1
        ^.case-at
          index.plus 1
  if. > @
    len.eq 0
    error "switch cases are empty"
    case-at 0

Here we're got an object – switch. switch decorates encapsulates an array of tuples, where each of them consists of 2 objects. First object – the condition, the second one – something that we have to return if condition was true.

I'm not sure that I can say what happens here cases.length > len!, but I can suppose that something like "alias" for our object – switch, and later we can get access to this value via ^.len.

Object case-at decorates encapsulates index of all tuples. If index equal to length of cases – returns true, otherwise execute next if. Next if object says that if case(i.e. tuple) has true at 0 index then we need to return tuple at 1, otherwise recursively return an object case-at with incremented index?

[maxonfjvipon]

@l3r8yJ you're right. But switch does not "decorates" tuple of tuples, it "encapsulates" it. The same story with recursive case-at