[Haskell-cafe] Trouble compiling Data.PriorityQueue?

Jaro Reinders jaro.reinders at gmail.com
Sat May 22 18:38:15 UTC 2021

Note that priority-queue is a pretty old package last uploaded in 2010 without 
very strict version bounds, so it is understandable that it doesn't compile 

I expect that fixing it would not be much work, but I think you will be better 
off using another priority queue package. Going by number of downloads psqueues 
and pqueue seem like good libraries.

On 22-05-2021 20:24, David Banas wrote:
> Has anyone else bumped into this compilation error when trying to use Data.PriorityQueue?
> Building library for priority-queue-0.2.1..
> [1 of 1] Compiling Data.PriorityQueue ( src/Data/PriorityQueue.hs, dist/build/Data/PriorityQueue.o )
> src/Data/PriorityQueue.hs:120:50-54: error:
>      Ambiguous occurrence ‘unzip’
>      It could refer to either ‘List.unzip’,
>                               imported from ‘Data.List’ at src/Data/PriorityQueue.hs:55:1-24
>                               (and originally defined in ‘GHC.List’)
>                            or ‘Seq.unzip’,
>                               imported from ‘Data.Sequence’ at src/Data/PriorityQueue.hs:54:1-27
>                               (and originally defined in ‘Data.Sequence.Internal’)
>      |
>  120 |             batches = map ((head *** fromList) . unzip) grouped
>      |                                                  ^^^^^
> cabal: Failed to build priority-queue-0.2.1 (which is required by exe:ex1 from
> haskarch- See the build log above for details.
> -db
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