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How to get a column in Haskell?

I am trying to find a non-exhaustive template in the library code. In particular, the implementation of HDBC mysql. It is trying to match the types in my program and map them to the mysql types that I consider. It seems I cannot get a column for this error, which means that since there are several parameters in the SQL query, it is difficult to determine what exactly causes it.

Is it possible to get a column in haskell so that I know which parameter is causing the error? I would also think that this should be caught by the compiler, as it should be able to look at my types and patterns and make sure there is an appropriate match.

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debugging haskell
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2 answers

You can use the GHCi debugger to determine where the exception from comes from .

I go through a complete example here .

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You can also check out the Debug.Trace library.

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