[Haskell-cafe] Re: Overloading functions based on arguments?

[John A. De Goes]

Chances are the program you're using to write your e-mails was written  
in C++ (or at least C), so don't knock it. :-)

In any case, no one has really addressed the original poster's  
question: No, "name overloading" is not possible in Haskell, and  
surprisingly, there are no blocking technical issues why this must be  
the case.

As a result of this limitation, we end up with abuse of type classes  
and endless synonyms, suffixes, and postfixes, and funky operators  
whose meanings must be inferred from documentation rather than  
convention.

Name overloading can certainly be abused, but in my opinion, the lack  
of it results in more problems than it eliminates.

Regards,

John A. De Goes
N-BRAIN, Inc.
The Evolution of Collaboration

http://www.n-brain.net    |    877-376-2724 x 101

On Feb 13, 2009, at 3:43 AM, Neil Mitchell wrote:

> Hi
>
>> Table is a table of name-value pairs I want to substitute in a tree- 
>> like
>> structure using:
>>
>> substitute :: Table -> Tree -> Tree
>>
>> For substituting a single name-value pair I want to define this  
>> utitlity
>> routine so I don't have to construct a Table all the time in the  
>> user code:
>>
>> substitute :: String -> Value -> Tree -> Tree
>
> Why not:
>
> substituteValue :: String -> Value -> Tree -> Tree
> substituteValue x y = substitute (table1 x y)
>
>> In the case I believe it would certainly be good to be able to name  
>> both
>> functions the same, but I fear I can not do so?  There are  
>> languages where
>> this is explicitelly allowed (e.g. C++ or Java), so I don't think  
>> it is such
>> an unuseful or evil thing.
>
> Languages like C++ and Java allow mutable state, object-orientated
> programming and require massively verbose code - all of which are
> unuseful and evil :-)
>
> I think this is a case of trying to apply C++/Java thoughts on to
> Haskell, you can map the concepts directly, but you really shouldn't.
> Try writing multiple methods with many names, or simple utility
> functions to convert between the cases, and it will go much nicer.
>
> Thanks
>
> Neil
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