[Haskell-cafe] Doubting Haskell

Jonathan Cast jonathanccast at fastmail.fm
Sun Feb 17 02:50:47 EST 2008

On 16 Feb 2008, at 11:46 PM, Anton van Straaten wrote:

> Colin Paul Adams wrote:
>>>>>>> "Cale" == Cale Gibbard <cgibbard at gmail.com> writes:
>>     Cale> So, the first version:
>>     Cale> import System.IO import Control.Exception (try)
>>     Cale> main = do mfh <- try (openFile "myFile" ReadMode) case mfh
>>     Cale> of Left err -> do putStr "Error opening file for reading: "
>>     Cale> print err Right fh -> do mline <- try (hGetLine fh) case
>>     Cale> mline of Left err -> do putStr "Error reading line: " print
>>     Cale> err hClose fh Right line -> putStrLn ("Read: " ++ line)
>> Left? Right?
>> Hardly descriptive terms. Sounds like a sinister language to me.
> I was thinking along the same lines.  Politically-sensitive left- 
> handed people everywhere ought to be offended that "Left" is the  
> alternative used to represent errors, mnemonic value notwithstanding.
> Is there a benefit to reusing a generic Either type for this sort  
> of thing?

Standardization.  It's already a standard, we need a standard sum  
type anyway, and it'd be kind of silly to have two isomorphic types  
with the same signature in the Prelude.


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