Only

The 1-tuple type or single-value "collection"

LTS Haskell 24.17:	0.1@rev:2
Stackage Nightly 2025-10-31:	0.1@rev:2
Latest on Hackage:	0.1@rev:2

See all snapshots Only appears in

BSD-3-Clause licensed by Herbert Valerio Riedel

Maintained by [email protected]

This version can be pinned in stack with:Only-0.1@sha256:c6033d181e0f802e9e8543f683fa9c50aeb01cfdf6c83cd5bb72fb47aa863b07,1398

Module documentation for 0.1

Data
- Data.Tuple
  - Data.Tuple.Only

Depends on 2 packages(full list with versions):

base, deepseq

Used by 6 packages in nightly-2025-10-30(full list with versions):

cassava, indexed-list-literals, optparse-generic, postgresql-simple, roc-id, sqlite-simple

This package provides a canonical anonymous 1-tuple type missing from Haskell for attaching typeclass instances.

NOTE: There is also the OneTuple package which by using a boxed data-type provides a 1-tuple type which has laziness properties which are more faithful to the ones of Haskell's native tuples; whereas the primary purpose of Only is to provide the traditionally so named type-wrapper for attaching typeclass instances.