exceptional: Essentially the Maybe type with error messages.

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This is a very simple type:

data Exceptional x
  = Failure String
  | Success x

It's much like Maybe, except instead of Nothing, we have Failure String.

A comparison could also be made to Either String. I made this library because I was dissatisfied with the Monad instance for Either. In this type, fail = Failure. It's rather simple.

Changes

0.3.0.0: Fix erroneous behavior in foldExceptional function added in version 0.2. This release actually does break (or rather fix) the foldExceptional function, so be careful.
0.2.0.0: Add exceptional function to encapsulate ordinary exceptions in the Exceptional monad. Add folding functions.

This release does not actually break the API, however I was rather tired when I chose the version number. This should be 0.1.6.

0.1.5.0: Add exceptIO function to encapsulate IO errors in the Exceptional monad.
0.1.4.3: Fix bug where exceptional won't compile on base < 4.8. Also move the changelog back to the description so it's more visible.
0.1.4.2: Moved change log to a separate file so Hackage displays it correctly.
0.1.4.1: Documentation enhancements/fixes.
0.1.4.0: Added fromMaybe and toMaybe functions, and a link to the bug tracker.
0.1.3.0: Fixed a typo. 0.1.2.0 won't build. Also added definition of empty for Alternative.
0.1.2.0: Added fromEither and toEither functions.
0.1.1.3: Hackage is terrible. Yet another formatting fix.
0.1.1.2: Yet another formatting fix.
0.1.1.1: Formatting fix to the haddock documentation.
0.1.1.0: Add runExceptional function.
0.1.0.1: Minor documentation changes. No changes to the API.
0.1.0.0: Initial version

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[Index]

Control
- Control.Exceptional

Downloads

exceptional-0.3.0.0.tar.gz [browse] (Cabal source package)
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Versions [RSS]	0.1.0.0, 0.1.0.1, 0.1.1.0, 0.1.1.1, 0.1.1.2, 0.1.1.3, 0.1.2.0, 0.1.3.0, 0.1.4.0, 0.1.4.1, 0.1.4.2, 0.1.4.3, 0.1.5.1, 0.2.0.0, 0.3.0.0 (info)
Dependencies	base (>=4 && <5), exceptions [details]
License	BSD-2-Clause
Copyright	Copyright (c) 2015, Peter Harpending.
Author	Peter Harpending
Maintainer	peter@harpending.org
Category	Control
Home page	https://github.com/
Bug tracker	https://github.com/pharpend/exceptional/issues
Source repo	head: git clone https://github.com/pharpend/exceptional.git -b master this: git clone https://github.com/pharpend/exceptional.git -b master(tag 0.3.0.0)
Uploaded	by pharpend at 2015-07-22T22:58:59Z
Distributions
Reverse Dependencies	1 direct, 0 indirect [details]
Downloads	11251 total (53 in the last 30 days)
Rating	(no votes yet) [estimated by Bayesian average]
Your Rating	λ λ λ
Status	Docs available [build log] Last success reported on 2015-07-22 [all 1 reports]

Readme for exceptional-0.3.0.0

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exceptional

This is a Haskell library that exists to house a type:

data Exceptional x
  = Failure String
  | Success x

It's much like Maybe, except instead of Nothing, we have Failure String.

A comparison could also be made to Either String. I made this library because I was dissatisfied with the Monad instance for Either. In this type, fail = Failure. It's rather simple.

Installing

cabal install exceptional

Or, add exceptional to the build-depends field in your .cabal file.