Simon,
That makes good sense, as it's hard to read code that contains standard terms used in a nonstandard way. I was just concerned that the function name I wanted to use was already in the Prelude! Perhaps the Prelude 'catch', I reasoned, could be called 'catchIO', since it is specific to the IO monad, allowing people to write their own 'catch'. Or 'catch' could be a member of a type class, which could be overloaded for any new monad.
But then I realized this argument could be made for practically every function in the Prelude. To dilute it with such abstraction would be a waste of resources. And there are loads of synonyms... I could use 'fling' and 'nab', 'punt' and 'snare', 'toss' and 'capture'....
Thanks for the point.
- Lyle
Simon Peyton-Jones wrote:
It's an explicit Haskell 98 design choice http://haskell.org/onlinereport/modules.html
"5.6.2 Shadowing Prelude Names
The rules about the Prelude have been cast so that it is possible to use Prelude names for nonstandard purposes; however, every module that does so must have an import declaration that makes this nonstandard usage explicit."
It's a decision one could debate, but it was an explicit choice.
Simon
| -----Original Message-----
| From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Lyle
| Kopnicky
| Sent: 12 August 2004 20:23
| To: Haskell Cafe
| Subject: [Haskell-cafe] Hiding functions
| | Hi all,
| | I'm working on a program that uses my own brand of exceptions, and I
| created two functions called 'throw' and 'catch'. In order for this
to
| work, I hide the Prelude 'catch' in my module, called 'Cont.hs'.
Thus:
| | module Cont where
| import Prelude hiding (catch)
| ...
| throw = ...
| catch = ...
| | This works hunky-dory until I create another file that imports Cont.
I
| get a conflict when I use 'catch', so I have to hide the Prelude one
again:
| | import Prelude hiding (catch)
| import Cont
| ...
| ... throw ...
| ... catch ...
| | So I'm a bit annoyed by this 'propagation' of hiding clauses. Then I
| created a new file, that redefined throw:
| | module ResumableExceptions where
| import Cont hiding (throw)
| import qualified Cont (throw)
| ...
| throw = ... Cont.throw ...
| | Finally, I created a file using ResumableExceptions:
| | import Cont hiding (throw)
| import ResumableExceptions
| ...
| ... throw ...
| | If I wanted to also use 'catch' I'd have to hide that from the Prelude
| as well.
| | I can't use type classes to solve this problem, because the types of
the
| two 'throw' functions are different.
| | Perhaps I should just make up new names for these things, eh? But
there
| might be code that uses 'throw' and doesn't really care which one is
| used, and it would be nice to just modify the import line and be done
| with it.
| | Any opinions?
| | Thanks,
| Lyle
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