Does there exist any sample code or other resources on writing a custom SQL-to-Haskell datatype converter instance for use with HDBC that would be accessible to someone just starting with Haskell? The reason I need this is because of this problem (using PostgreSQL): Prelude Database.HDBC.PostgreSQL Database.HDBC> res <- (quickQuery db "select 1::numeric(5,4);" []) Prelude Database.HDBC.PostgreSQL Database.HDBC> res [[SqlRational (1 % 1)]] Prelude Database.HDBC.PostgreSQL Database.HDBC> res <- (quickQuery db "select 1::numeric(5,0);" []) [[SqlRational (1 % 1)]] where db is a database connection. The SQL values 1::numeric(5,4) and 1::numeric(5,0) are supposed to be fixed-precision numbers having 4 and zero significant decimal figures after the decimal point, respectively. Both are offered by HDBC as the same SqlValue, SqlRational (1 % 1) but they are not really the same at all. The precision information has been lost. The native outputs of PostgreSQL, before HDBC's type conversion, are 1.0000 and 1 for 'select 1::numeric(5,4);' and 'select 1::numeric(5,0);', respectively. -- Henry House