Scala：从seq到元组

Question

It is very easy to convert a tuple into a List/Seq by doing:

myTuple.productIterator.toSeq

But what about the reverse operation (just out of curiosity). The code below works, but is quite ugly...

def arrayToTuple(a: Seq[Any]) = a.size match {
    case  1 => (a(0))
    case  2 => (a(0), a(1))
    case  3 => (a(0), a(1), a(2))
    case  4 => (a(0), a(1), a(2), a(3))
    case  5 => (a(0), a(1), a(2), a(3), a(4))
    case  6 => (a(0), a(1), a(2), a(3), a(4), a(5))
    case  7 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6))
    case  8 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7))
    case  9 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8))
    case 10 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9))
    case 11 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9), a(10))
    case 12 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9), a(10), a(11))
    case 13 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9), a(10), a(11), a(12))
    case 14 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9), a(10), a(11), a(12), a(13))
    case 15 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9), a(10), a(11), a(12), a(13), a(14))
    case 16 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9), a(10), a(11), a(12), a(13), a(14), a(15))
    case 17 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9), a(10), a(11), a(12), a(13), a(14), a(15), a(16))
    case 18 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9), a(10), a(11), a(12), a(13), a(14), a(15), a(16), a(17))
    case 19 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9), a(10), a(11), a(12), a(13), a(14), a(15), a(16), a(17), a(18))
    case 20 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9), a(10), a(11), a(12), a(13), a(14), a(15), a(16), a(17), a(18), a(19))
    case 21 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9), a(10), a(11), a(12), a(13), a(14), a(15), a(16), a(17), a(18), a(19), a(20))
    case 22 => (a(0), a(1), a(2), a(3), a(4), a(5), a(6), a(7), a(8), a(9), a(10), a(11), a(12), a(13), a(14), a(15), a(16), a(17), a(18), a(19), a(20), a(21))
    case  _ => (0)
  }

Answer 1

This is not possible in Scala 2.X because each length of tuple is a different type and each element of a tuple has a different type. So it would be difficult to write a function to append a value of any type to a tuple of any type.

But to satisfy your curiosity, this is a pending feature of Scala 3:

Tuples with arbitrary numbers of elements are treated as sequences of nested pairs. Eg (a, b, c) is shorthand for (a, (b, (c, ()))) . This lets us drop the current limit of 22 for maximal tuple length and it allows generic programs over tuples analogous to what is currently done for HList .

See http://dotty.epfl.ch/docs/reference/overview.html