#4359: Implement lambda-case/lambda-if
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Reporter: batterseapower | Owner:
Type: feature request | Status: new
Priority: normal | Milestone: 7.4.1
Component: Compiler | Version: 7.1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Changes (by illissius):
* cc: illissius@… (added)
Comment:
> the downside is that we have to adjust our mental parsers/typecheckers
to recognise if then and case of as a lambda, and I'm not sure the gain in
brevity is worth the loss of readability
> My own gut feel is that it's a lot better to have an initial symbol to
say "here comes a function".
I don't think I agree with this. Maybe the word 'lambda' in the name of
the proposal is misleading; I don't think the intuition here should be
that of a lambda. I think it should be (and was originally) partial
application. I think it's very natural for any Haskell programmer that if
you have a function, and you apply it less than fully, that what you end
up with is a function. The only difference here is that the argument sits
in between the 'case of' rather than after the name of the function, but I
don't think that's a big obstacle; it's universally obvious that case-of
is special. I think the originally proposed 'case of' syntax is elegant
and intuitive.
I'm much more ambivalent about if-then-else. It would make sense for
completeness's sake, but it's a lot uglier (due to having multiple
unorthodoxly-positioned arguments) and I don't see nearly as much of a use
case. (It also, unlike 'case of', doesn't feel intuitive -- this is just a
gut feel and I don't really have any arguments to explain why, but then
again, the only real definition of intuitivity is whether people feel that
way...) I think I'd rather just put ifThenElse in the Prelude and have
people use that if they want to partially apply it (which isn't possible
with case-of).
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4359#comment:18>
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