discrete: replacement for enum
A Discrete
type is a set X with at least one element, along with two
functions,
and succ
:: X -> Maybe
X
,
such that all inhabitants of the set X can be constructed given at least
a single element of the set and these two functions. The following must hold:pred
:: X -> Maybe
X
pred
>=>
succ
>=>
pred
=pred
succ
>=>
pred
>=>
succ
=succ
This means that Int
is a discrete type, because given any x :: Int
, one
can construct any other Int
with the following functions:
succ
x = if x==
maxBound
thenNothing
elseJust
(x+
1)
pred
x = if x==
minBound
thenNothing
elseJust
(x-
1)
This also means that something like Double
is not a discrete type, because
there are no such functions succ
and pred
that given any value of type Double
can allow the construction of all values of type Double
.
Discrete
acts as a replacement for GHC.Enum.Enum
. The motivation for
Discrete
is two-fold: firstly, totality of all typeclass instances, and
secondly, that GHC.Enum.Enum
is a typeclass that does too many things,
and does them poorly. If succ
or pred
are called on maxBound
or minBound
, respectively, the result will be Nothing
.
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- Package description (revised from the package)
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Versions [RSS] | 0.1.0.0 |
---|---|
Change log | ChangeLog.md |
Dependencies | base (>=4.7 && <4.13) [details] |
License | BSD-3-Clause |
Author | chessai |
Maintainer | chessai1996@gmail.com |
Revised | Revision 1 made by chessai at 2018-09-17T18:35:30Z |
Category | Data |
Home page | https://github.com/chessai/discrete |
Uploaded | by chessai at 2018-09-17T17:24:12Z |
Distributions | |
Reverse Dependencies | 1 direct, 0 indirect [details] |
Downloads | 778 total (2 in the last 30 days) |
Rating | (no votes yet) [estimated by Bayesian average] |
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Status | Docs available [build log] Last success reported on 2018-09-17 [all 2 reports] |