monad-logger question

[Luke Evans]

I was trying to convert the function:

runDB connStr = runResourceT . runStderrLoggingT . withSqliteConn connStr . runSqlConn

...to take a Bool argument that would then switch between runStderrLoggingT and runNoLoggingT.  

Unfortunately, these involve different concrete types for the logger.  

I suspect this is life telling me that I need to strengthen my Haskell type-wrangling muscles, but anyway...

Can someone point me in the right direction?

Thanks!

-- Luke

[Michael Snoyman]

If you look at LoggingT, you'll see that it has a function for how to log a message. If you provide a function which does nothing, it would be functionally identical to NoLoggingT. So you could write a function like:

runFakeLoggingT (LoggingT f) = f $ \_ _ _ _ -> return ()

Then you could choose between runStderrLoggingT and runFakeLoggingT based on your Bool parameter.

-- Luke

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[Luke Evans]

Thanks again Michael.  I was slowly coming to that conclusion, but sometimes faced with what looks like official and ready-made items, you just keep trying the round block in the square hole ;-)