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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

0.1.4.3
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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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) [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/pharpend/exceptional
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 0.1.4.3)
Uploaded by pharpend at 2015-05-18T03:27:59Z
Distributions
Reverse Dependencies 1 direct, 0 indirect [details]
Downloads 10954 total (38 in the last 30 days)
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Status Docs uploaded by user
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Readme for exceptional-0.1.4.3

[back to package description]

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.