The origami package

[Tags:bsd3, library, test]

The Origami package consists of a coding pattern for transforming heterogenously typed data and Template Haskell macros to support the pattern. It operates in the same problem space as SYB, but generates the boilerplate for the user.

In the pattern, we focus on a specific set of types, the fold family. For each constructor of each of those types, the user will define a function to replace the constructor when folding.

These functions are collected together into a single record. (Its declaration is generated for the user.) Collecting the functions together forces the typing of all the functions to remain consistent and facilitates code reuse.

For each datatype, a fold function is automatically generated that applies the fold record to values of that datatype. It decomposes the value into parts according to its constructor, recursively applies the fold to the parts, then puts them back together using the replacement constructor function from the record.

As with SYB, Origami lets the user think on a higher-level of abstraction about data transformation and relieves her from the need to write boilerplate.

See the website for more information and examples.


Versions 0.0.1, 0.0.2, 0.0.3, 0.0.4, 0.0.5, 0.0.6
Change log changelog
Dependencies base (==4.*), bifunctors (>=4), containers (>=0.5), lens (>=4), mtl (>=2.1), pretty (>=1.1), template-haskell [details]
License BSD3
Copyright (c) 2015 Eric Nedervold
Author Eric Nedervold<>
Maintainer Eric Nedervold<>
Category Data
Home page
Bug tracker
Source repository head: git clone git://
Uploaded Sat Oct 24 13:57:03 UTC 2015 by nedervold
Distributions NixOS:0.0.6
Downloads 671 total (13 in the last 30 days)
0 []
Status Docs available [build log]
Last success reported on 2015-10-24 [all 1 reports]
Hackage Matrix CI




Maintainer's Corner

For package maintainers and hackage trustees