Pointless Haskell
Introduction
Pointless Haskell is library for point-free programming with recursion patterns defined as hylomorphisms. It is part of the
UMinho Haskell Libraries that are being developed in the
Research.PURe project. The core of the library is described in the following paper.
It also allows the visualization of the intermediate data structure of the hylomorphisms with
GHood. This feature toghether with the
DrHylo tool allows us to easily visualize recursion trees of Haskell functions. We first implemented this ideas using
Generic Haskell, as presented in WFLP'03. We now take a different approach to genericity based on
Personal/Alcino.PolyP.
Download
The latest snapshot of the UMinho Haskell Libraries can be downloaded
here. The modules that comprise Pointless Haskell are the following.
Module | Description |
Pointless.Combinators | Point-free programming combinators. |
Pointless.Combinators.Uncurried | Point-free definitions of uncurried versions of the basic combinators. |
Pointless.Isomorphisms | Auxiliary isomorphism definitions. |
Pointless.Functors | Definition of functors, generic maps, and sum-of-products representation. |
Pointless.RecursionPatterns | Definition of the typical recursion as hylomorphisms. |
Pointless.Observe.Functors | Definition of generic observations. |
Pointless.Observe.RecursionPatterns | Recursion patterns with observation of intermediate data structures. |
Pointless.Examples.Examples | Lots of examples. |
Debug.Observe | Slightly modified GHood library. |
Usage
For the moment there is no documentation, but by reading the papers and looking at examples you should be able to learn it by yourself. It was only tested on GHC. I think that it should be easy to use it under Hugs.
Please send feedback to
alcino@di.uminho.pt.
Introduction
Tool for deriving hylomorphisms from a restricted Haskell syntax. It is based on the algorithm first presented in the paper
Deriving Structural Hylomorphisms From Recursive Definitions at ICFP'96 by Hu, Iwasaki, and Takeichi.
Download
See
PUReSoftware.
Usage
To use
DrHylo, simply type
DrHylo -h
at the command line, and follow instructions.
Usage: Personal/Alcino.DrHylo [OPTION...]
-o[FILE] --output[=FILE] output FILE
-i[FILE] --input[=FILE] input FILE
To run the resulting Haskell files you will need
PointlessHaskell.
Please send feedback to
alcino@di.uminho.pt.
Point-free Program Transformation
This is a project where I,
José Proença, worked on since April until October 2005. It was supervised by
Jorge Sousa Pinto and
Alcino Cunha, who supported and helped me during this time. The proposal is explained in more detailed in
here. The results can be found in my internship report,
here.
The project consists on two parts:
- Definition of two refactorings -- the conversion from point-wise to pointfree and the removal of guards;
- Automatic simplification and transformation of pointfree expressions.
Refactorings in HaRe
In the begining of the project, I spent two weeks in Canterbury developing two refactorings to be part of
HaRe:
A snapshot of the source code where these transformations are applied can be found
here.
There are also some examples that can be found in the following links:
The SimpliFree Tool
Allows for the automatic simplification and some program transformation of Haskell code, written in a point-free style. The technical report is available
here. The SimpliFree tool is now available in the Uminho Haskell Libraries, that can be downloaded from the
CVS repository.
This tool uses Haskell pattern matching to apply rules, by creating an auxiliary file with the functions where the strategies, rules and the pointfree terms are defined. In spite of the fact that this approach meant to be simpler than most approaches where a pattern matching algorithm is defined, the definitions of functions that apply a rule were more complex than expected.
In September, this tool, together with the DrHylo tool and the Pointless library, were presented in IFL'05 workshop.
The presentation "A Framework for Point-free Program Transformation", shown in this workshop, can be found
here.
The SimpliFree tool was also presented in the PURe Workshop 2005. The slides can be found
here.