#836: rebindable if-then-else syntax
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Reporter: nibro | Owner:
Type: feature request | Status: new
Priority: normal | Milestone: _|_
Component: Compiler (Parser) | Version: 6.13
Keywords: | Testcase: N/A
Blockedby: | Difficulty: Unknown
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Changes (by vivian):
* cc: haskell.vivian.mcph...@… (added)
* failure: => None/Unknown
* version: 6.4.2 => 6.13
* component: Compiler => Compiler (Parser)
Comment:
The do notation is syntactic sugar on top of (>>=) and return.
Why not syntactic sugar for "if ... then ... else."
With language Extension 'OverlappingInstances' it is possible to have a
default definition
{{{
class IfThenElse a where
if_then_else :: Bool -> a -> a -> a
instance IfThenElse a where
if_then_else b t f = case b of
True -> t
False -> f
}}}
And then monads such as LogicT
[http://hackage.haskell.org/package/logict-0.2.1] and other code regions
with a requirement for custom ifte can overload their own.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/836#comment:5>
GHC <http://www.haskell.org/ghc/>
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