How to define Tuple1 in Scala?

Question

I try to use (1,), but doesn't work, what's the syntax to define Tuple1 in scala ?

scala> val a=(1,)
<console>:1: error: illegal start of simple expression
       val a=(1,)

Answer 1

For tuple with cardinality 2 or more, you can use parentheses, however for with cardinality 1, you need to use Tuple1:

scala> val tuple1 = Tuple1(1)
tuple1: (Int,) = (1,)

scala> val tuple2 = ('a', 1)
tuple2: (Char, Int) = (a,1)

scala> val tuple3 = ('a', 1, "name")
tuple3: (Char, Int, java.lang.String) = (a,1,name)

scala> tuple1._1
res0: Int = 1
scala> tuple2._2
res1: Int = 1
scala> tuple3._1
res2: Char = a
scala> tuple3._3
res3: String = name

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To declare the type, use Tuple1[T], for example val t : Tuple1[Int] = Tuple1(22)