Performing operations on (specifically how to add a List of) Long in Scala
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05-07-2019 - |
Question
I've tried a number of techniques, but I keep bumping into
(fragment of wtf.scala):3: error: overloaded method value + with alternatives
(Int)Int <and> (Char)Int <and> (Short)Int <and> (Byte)Int cannot be applied to (Long)
in one way or another. As an example, here are two functions to reproduce the problem. sumInt works fine... but sumLong errors. I don't get it.
// compiles (and works) fine
def sumInt(list: List[Int]): Int = list.foldLeft(0)(_ + _)
// compile time error. no + define on Long? I don't get it
def sumLong(list: List[Long]): Long = list.foldLeft(0)(_ + _)
Solution
You need to make the 0 a Long constant: "0L":
scala> def sumLong(list: List[Long]): Long = list.foldLeft(0L)(_ + _)
sumLong: (List[Long])Long
scala> scala> sumLong(List(1L, 2L, 3L))
res2: Long = 6
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