Add Pair-based edges initializer to Graph types #198

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1. jsbean commented on Nov 3, 2018

   

   jsbean

   on Nov 3, 2018

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   I think this would require an initializer like so:

   extension WeightedGraph where Node == Tendency, Weight == Int {
       init <D> (_ nodes: Set<Tendency>, _ dictionaryLiteral: D) where D: DictionaryLiteral, where D.Element == (Tendency,Int) 
       {
           ...
       }
   }
2. jsbean commented on Nov 3, 2018

   

   jsbean

   on Nov 3, 2018

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   See DictionaryLiteral and KeyValuePairs.

   You can't actually pass a real dictionary in, because tuples are not Hashable 🤦‍♂️ .
3. jsbean commented on Nov 3, 2018

   

   jsbean

   on Nov 3, 2018

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   But if this is for syntax sugar, then you can use the DictionaryLiteral syntax.

   Give it a try. No guarantees here.
4. bwetherfield commented on Nov 3, 2018

   

   bwetherfield

   on Nov 3, 2018

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   Oh! Totally forgot about Hashability!
5. jsbean commented on Nov 3, 2018

   

   jsbean

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   But KeyValuePairs doesn't actually require Hashable conformance :o, I am pretty sure.
6. jsbean commented on Nov 3, 2018

   

   jsbean

   on Nov 3, 2018

   Last edited by jsbean

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   You would need to do something like:

   extension WeightedGraph {
       init (_ nodes: Set<Tendency>, _ keyValuesPairs: KeyValuePairs<Node,Weight>) {
           self.init(nodes, Dictionary(keyValuePairs.lazy.map { k,v in (UnorderedPair(k.0, k.1), v) })
       }
   }