Difference between revisions of "The Other Prelude"
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Although, not Haskell 98, hierarchical modules will definitely be in Haskell'. We take it for granted. |
Although, not Haskell 98, hierarchical modules will definitely be in Haskell'. We take it for granted. |
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* <hask>TheOtherPrelude</hask> - Minimalistic module. |
* <hask>TheOtherPrelude</hask> - Minimalistic module. |
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− | * <hask>TheOtherPrelude. |
+ | * <hask>TheOtherPrelude.Utilities</hask> - Convenient definitions. The reasoning behind its existence is that we want the Prelude to be very concise. It should not steal good names. |
== Open Issues == |
== Open Issues == |
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The imaginery Prelude as it stands, |
The imaginery Prelude as it stands, |
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+ | === <hask>TheOtherPrelude</hask> === |
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− | |||
<haskell> |
<haskell> |
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+ | -- module: TheOtherPrelude |
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import Prelude () -- hide everything |
import Prelude () -- hide everything |
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</haskell> |
</haskell> |
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+ | === <hask>TheOtherPrelude.Utilities</hask> === |
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+ | <haskell> |
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+ | -- module: TheOtherPrelude.Utilities |
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+ | |||
+ | import Prelude () -- hide everything |
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+ | |||
+ | -- this is the if-then-else proposal |
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+ | -- the name has been chosen to reflect the magic of Church booleans! |
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+ | boolean True x _ = x |
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+ | boolean False _ y = x |
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+ | |||
+ | </haskell> |
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== How To Use == |
== How To Use == |
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<haskell> |
<haskell> |
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* [[Prelude extensions]] and [[Prelude function suggestions]] - Unlike ''The Other Prelude'' they ''enhance'' the Prelude. |
* [[Prelude extensions]] and [[Prelude function suggestions]] - Unlike ''The Other Prelude'' they ''enhance'' the Prelude. |
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* [[Functor hierarchy proposal]] - Making <hask>Monad m</hask> imply <hask>Functor m</hask> (adopted by ''The Other Prelude''). |
* [[Functor hierarchy proposal]] - Making <hask>Monad m</hask> imply <hask>Functor m</hask> (adopted by ''The Other Prelude''). |
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− | * [[If-then-else]] - Making <hask>if</hask> a function. |
+ | * [[If-then-else]] - Making <hask>if</hask> a function (partially adopted by ''The Other Prelude'', we are silent on the bigger issue of sugar). |
* [http://software.complete.org/missingh/static/doc/ MissingH] - Functions "missing" from the Haskell Prelude/libraries. |
* [http://software.complete.org/missingh/static/doc/ MissingH] - Functions "missing" from the Haskell Prelude/libraries. |
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* [[MonadPlus reform proposal]] - Clarifies ambiguities around MonadPlus laws (adopted by ''The Other Prelude'') |
* [[MonadPlus reform proposal]] - Clarifies ambiguities around MonadPlus laws (adopted by ''The Other Prelude'') |
Revision as of 06:15, 30 December 2006
Call For Contribution
This fun project, called The Other Prelude, is a creative reconstruction of the standard Prelude. By disregarding history and compatibility, we get a clean sheet.
Committee
This project has no committee whatsoever. Haskell community discussed the issues here.
Naming Conventions
- Function names should be easy for beginners to consume.
- Specifically, The Other Prelude naming convention is to use
- descriptive symbols for functions that are naturally infix (e.g.,
mplus
is replaced by(++)
) - whole English words and camelCase for functions (e.g.,
orElse
but notfmap
)
- descriptive symbols for functions that are naturally infix (e.g.,
The Hierarchy
Although, not Haskell 98, hierarchical modules will definitely be in Haskell'. We take it for granted.
TheOtherPrelude
- Minimalistic module.TheOtherPrelude.Utilities
- Convenient definitions. The reasoning behind its existence is that we want the Prelude to be very concise. It should not steal good names.
Open Issues
- Should Prelude functions use
Integer
instead ofInt
? - Should
String
be a class rather than a type synonym?
The Code
Currently, the code is in Wiki form. If people do agree that the collaborative decisions begot something pretty, we'll have a group of files in darcs.haskell.org some time.
The imaginery Prelude as it stands,
TheOtherPrelude
TheOtherPrelude
-- module: TheOtherPrelude
import Prelude () -- hide everything
-- the idea is to remove 'fmap'.
-- both map :: (a -> b) -> [a] -> [b] ('fmap' for the monad [])
-- and (.) :: (a -> b) -> (e -> a) -> (e -> b) ('fmap' for the (->) e monad)
-- are good names, and are intuitively prefix and infix respectively.
class Functor f where
-- 'fmap' is guilty of nothing but a bad name
map, (.) :: (a -> b) -> f a -> f b
-- implementing either is enough
map = (.)
(.) = map
-- the following has been shamelessly copied,
-- from the [[Functor hierarchy proposal]] wiki page.
class Functor f => Applicative f where
-- lifting a value
return :: a -> f a
-- should this be named 'ap'? is 'ap' a good name?
-- can you come up with a better name?
-- can it refactor the liftM* type gymnastics?
(<*>) :: f (a -> b) -> f a -> f b
-- this leaves little left for the actual Monad class
class (Applicative m) => Monad m where
-- the binding operation, gist of a monad
(>>=) :: m a -> (a -> m b) -> m b
-- throwing out the outer monad
join :: m (m a) -> m a
-- when the second is independent of the first
-- included in the class in case performance can be enhanced
(>>) :: m a -> m b -> m b
-- intuitive definitions
fa >> fb = (map (const id) fa) <*> fb -- is there a better definition?
x >>= f = join (map f x)
join x = x >>= id
-- we shamelessly copy from the [[MonadPlus reform proposal]] now.
-- zero will be used when pattern matching against refutable patterns in
-- do-notation as well as to provide support for monad comprehensions.
-- should satisfy 'left zero': zero >>= f = zero
class (Monad m) => MonadZero m where
zero :: m a
-- should satisfy 'monoid'
-- zero ++ b = b, b ++ zero = b, (a ++ b) ++ c = a ++ (b ++ c)
-- and 'left distribution'
-- (a ++ b) >>= f = (a >>= f) ++ (b >>= f)
class (MonadZero m) => MonadPlus m where
(++) :: m a -> m a -> m a
-- should satisfy 'monoid'
-- zero `orElse` b = b, b `orElse` zero = b
-- (a `orElse` b) `orElse` c = a `orElse` (b `orElse` c)
-- and 'left catch'
-- (return a) `orElse` b = a
class (MonadZero m) => MonadOr m where
orElse :: m a -> m a -> m a
TheOtherPrelude.Utilities
TheOtherPrelude.Utilities
-- module: TheOtherPrelude.Utilities
import Prelude () -- hide everything
-- this is the if-then-else proposal
-- the name has been chosen to reflect the magic of Church booleans!
boolean True x _ = x
boolean False _ y = x
How To Use
-- ''The Other Prelude'' is an alternative, not a replacement.
-- So we need to hide everything from the Prelude
import Prelude ()
-- This is just an example assuming there is nothing to hide
import TheOtherPrelude
-- Hopefully, this module will contain lift,...
-- Standard convention is to use M.lift (instead of liftM)
import qualified TheOtherPrelude.Monad.Kleisli as M
See also
- Mathematical prelude discussion - A numeric Prelude in good shape already. Will a merger be ever possible?
- Prelude extensions and Prelude function suggestions - Unlike The Other Prelude they enhance the Prelude.
- Functor hierarchy proposal - Making
Monad m
implyFunctor m
(adopted by The Other Prelude). - If-then-else - Making
if
a function (partially adopted by The Other Prelude, we are silent on the bigger issue of sugar). - MissingH - Functions "missing" from the Haskell Prelude/libraries.
- MonadPlus reform proposal - Clarifies ambiguities around MonadPlus laws (adopted by The Other Prelude)