Tuplet implements tuple-like heterogeneous vectors over a type constructor, providing arity-generic operations. A tuplet constructor of arity n represents a (α₁ * ... * αₙ) tuplet as α₁ elt * ... * αₙ elt. Generic operations on tuples takes the from of shape-preserving transformations or shape-agnostic reductions, which accept callbacks acting generically on a component of type α elt.

In practise, the Tuplet library is useful for dealing with representations of tuples in GADTs, since it eliminates treating each arity as a special case. In particular a GADT α t may be extended with a single additional constructor and related code to support cases of the form (α₁ * ... * αₙ) t up to the arity supported by Tuplet.

Recursive type definitions are supported by using recursive modules, where tuple parts of the signature can be included. Also a helper module can provide constructor aliases for the main type. Thus, no arity-specific code should be needed outside the Tuplet library.

See test_recursive.ml for an example.