Hi all, There are a few things that I don't understand involving Data.Text and instance declarations... I'm building a small web app to practise Haskell and am using the SQLite.Simple library. I have defined a few types and functions like so: ''' data BookmarkDB = BookmarkDB Connection Table newtype Table = Table Text instance ToField Table where toField = SQLText initDB :: FilePath -> Table -> IO BookmarkDB initDB fp table = do let query = Query ("CREATE TABLE IF NOT EXISTS :table " <> " (url TEXT, tags TEXT, date INTEGER)") conn <- open fp executeNamed conn query [":table" := table] return $ BookmarkDB conn table ''' 1. My first question is about the instance declaration. Why would ''' instance ToField Table where toField = SQLText ''' return this error ? ''' Couldn't match type ‘Table’ with ‘Text’ Expected type: Table -> SQLData Actual type: Text -> SQLData • In the expression: SQLText In an equation for ‘toField’: toField = SQLText In the instance declaration for ‘ToField Table’ ''' I've noticed that if I write ''' instance ToField Table where toField (Table t) = SQLText t ''' I have no error and it compiles. I don't get it, what is 'toField' supposed to receive except a Table? 2. My second question is concerning the initDB function. If I write it that way, the code compiles, but I get an error during execution: bkmrk: SQLite3 returned ErrorError while attempting to perform prepare "CREATE TABLE IF NOT EXISTS :table (url TEXT, tags TEXT, date INTEGER)": near ":table": syntax error I don't understand what is wrong with the code and I doubt that my query is wrong because everything works with the last code snippet I wrote (see question #3). 3. Trying to get around the error I've noticed a few things. If I try to write this instead: ''' initDB :: FilePath -> Table -> IO BookmarkDB initDB fp table = do let query = Query ("CREATE TABLE IF NOT EXISTS " <> table <> " (url TEXT, tags TEXT, date INTEGER)") conn <- open fp execute_ conn query return $ BookmarkDB conn table ''' it doesn't compile because table is of type Table and not Data.Text.Internal.Text, which I get, but I don't know what is the Haskell way of resolving this. I've also noticed that this will help: ''' initDB :: FilePath -> Table -> IO BookmarkDB initDB fp t@(Table table) = do let query = Query ("CREATE TABLE IF NOT EXISTS " <> table <> " (url TEXT, tags TEXT, date INTEGER)") conn <- open fp execute_ conn query return $ BookmarkDB conn t ''' But I *really* don't get why! The most confusing part for me is that the last initDB function will do exactly what I want it to do, but I am unable to understand why it works...Why am I able to concatenate the 'table' now and not before and why is 't' of a different type than 'table'? All of this is very confusing and I find myself unable to reason about it. Sorry if this is a big/messy question. I hope everything is clear enough to answer... Thank you all!