Data.Ratio and exceptions

[Simon Marlow]

On 14/06/2012 02:27, wren ng thornton wrote:
> On 6/13/12 6:57 AM, Simon Hengel wrote:
>>> I'll go ahead and make this change. Thanks for the suggestion!
>>
>> I agree that ArithException feels more appropriate here. But I make two
>> observations:
>>
>> (1) It replaces specific error messages with less specific ones.
>>
>> The error message will not include the function/operator name
>> anymore, e.g.:
>>
>> ghci> 1 % 0
>> *** Exception: Ratio.%: zero denominator
>>
>> would become:
>>
>> ghci> 1 % 0
>> *** Exception: divide by zero
>
> That's no good. I wonder whether ArithExceptions should be given their
> code location a la assertion failures[1]. Probably all the built-in
> exception types should do so.
>
>
> [1] http://www.haskell.org/ghc/docs/7.4.1/html/users_guide/assertions.html

But that wouldn't help - you'd just get a code location somewhere deep 
in the base package every time.

So we could make a separate RatioZeroDenominator exception, and add that 
to ArithException.  That would mean no loss of information relative to 
the current state of affairs.

Cheers,
	Simon