ios - What is the purpose of a DictionaryIndex in Swift? -


per header documentation on dictionary in swift:

a hash-based mapping key value instances. collection of key-value pairs no defined ordering.

note in particular- no defined ordering.

with in mind, i'm having trouble understanding these computed variables (and related methods take these types):

// position of first element in non-empty dictionary.   var startindex: dictionaryindex<key, value> { }  // collection's "past end" position. var endindex: dictionaryindex<key, value> { }

the "index" here dictionaryindex.

however, documentation on dictionaryindex kinda circular here:

used access key-value pairs in instance of dictionary<key, value>.

what purpose of dictionaryindex?

we know dictionary composed of keys , values. every key mapped value based on internal calculations. here mechanism used purpose hashing.

from wikipedia:

a hash table uses hash function compute index array of buckets or slots, correct value can found.

consider dictionary hash table, uses hash function , returns object of type dictionaryindex - using can access particular object directly in dictionary.

correct me if wrong!


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