Well, there obviously is a problem in your example code. The argument "tableName" does not live in the world of types, so /SqlExpr (Entity tableName)/ is meaningless (this barrier is getting fuzzier with each version of GHC, but well...). Perhaps something can be done with existential types ? Le 24/11/12 12:07, Erik de Castro Lopo a écrit :
Hi all,
Below my .sig is a little Persist/Esqueleto program that works correctly.
The getUserCount function does thr right thing and returns the number of rows in the User table. However, what I'd like is a generic function that returns the row count of any table, something vaguely like this:
queryRowCount :: tableType -> SqlPersist IO Int64 queryRowCount tableName = do [Value x] <- select . from $ \(_ :: SqlExpr (Entity tableName)) -> return countRows return x
Is there any way to do this? Its probably possible in Agda, but can it be made to work with GHC?
Cheers, Erik