Question

Why I can’t construct large tuples in Haskell? Why there’s a tuple size limit?

Prelude> (1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)

<interactive>:1:0:
    No instance for (Show
                       (t,
                        t1,
                        t2,
                        ...
                        t23))
      arising from a use of `print' at <interactive>:1:0-48
    Possible fix:
      add an instance declaration for
      (Show
         (t,
          t1,
          t2,
          ...
          t23))
    In a stmt of a 'do' expression: print it

Answer 1

Tuples can be of arbitrary length*, but Show, as well as Eq, Ord, Read, Bounded, etc are only instantiated up to 15-tuple. From the Haskell 98 report §6.1.4:

There is no upper bound on the size of a tuple, but some Haskell implementations may restrict the size of tuples, and limit the instances associated with larger tuples. However, every Haskell implementation must support tuples up to size 15, together with the instances for Eq, Ord, Bounded, Read, and Show. The Prelude and libraries define tuple functions such as zip for tuples up to a size of 7.

As others have said, if you need a 24-tuple, you should use a better data structure.

---

Edit: * as of GHC 6.12.2, the maximum size of a tuple is 62:

Prelude> :t (1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8)

<interactive>:1:0:
    A 64-tuple is too large for GHC
      (max size is 62)
      Workaround: use nested tuples or define a data type