solved: implementation dependent (was Re: [Haskell-beginners] better way to create Array defined on all indices

Larry Evans cppljevans at
Thu Oct 16 10:17:40 EDT 2008

On 10/15/08 23:50, Larry Evans wrote:
> On 10/15/08 16:05, Larry Evans wrote:
>> I'd like to have an Array indices values
>> (see
>> defined on [minBound::indices ... maxBound::indices].
> The aforementioned array.html has:
>                             _     -> error "Array.!: \
>                                            \multiply defined array element")
> suggesting it should detect redefinitions; 

> Is this a bug in my ghc library?
According to:

it's not.  It's just implemented differently by libraries:

> The Haskell 98 Report further specifies that if any two associations 
> in the list have the same index, the value at that index is undefined 
> (i.e. bottom). However in GHC's implementation, the value at such an 
> index is the value part of the last association with that index in the 
> list. 
So, if I want multiple definitions diagnosed as an error, I'll have to 
do it myself :(

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