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scala> val set = scala.collection.mutable.Set[(Int, Int)]()
set: scala.collection.mutable.Set[(Int, Int)] = Set()
scala> set += (3, 4)
<console>:9: error: type mismatch;
found : Int(3)
required: (Int, Int)
set += (3, 4)
^
scala> set += Tuple2(3, 4)
res5: set.type = Set((3,4))
Adding (3, 4) does not work - why ?
Normally, (3, 4) also represents a tuple with two elements.
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You can also add tuples to a set. And like normal elements, you can add the same tuple only once.
Creating a Tuple A tuple is created by placing all the items (elements) inside parentheses () , separated by commas. The parentheses are optional, however, it is a good practice to use them. A tuple can have any number of items and they may be of different types (integer, float, list, string, etc.).
Only two operations are allowed on tuple , as shown below. Operations like insert / delete at an index is not allowed. I learnt that tuple is an immutable data model. list allows insert and delete operations.
The issue is that it exists in the Set trait a method +(elem1: A, elem2: A, elems: A+) and the compiler is confused by it. It actually believes that you try to use this method with 2 Int parameters instead of using it with a tuple, as expected.
You can use instead: set += (3 -> 4) or set += ((3, 4))
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