Karle,
The expression (t,d,y) must have type Pkg, by your type annotation for
update_table1, so [ (t,d,y) ] has type [Pkg]. Also by your type
annotation, the result of update_table1 should by of type Table. Is
the type [Pkg] compatible with type Table? In other words, is the type
[ (Pkgtype,Address,Payload) ] the same as the type [ (Address,Port) ]?
Judging from your questions yesterday and today, I suspect that you
have not worked carefully through a Haskell language tutorial. I would
not discourage you from asking questions on the mailing list, but I
would strongly encourage you to consider referring to some of the
resources at http://haskell.org/haskellwiki/Books_and_tutorials before
trying to proceed with whatever programming project you are working
on.
Regards,
Chris
On 11/2/07, karle
The same declaration.-
type Address = Int data Port = C | D deriving(Eq,Show) data Payload = UP[Char] | RTDP(Address,Port) deriving(Eq,Show) data Pkgtype = RTD | U deriving(Eq,Show) type Pkg = (Pkgtype,Address,Payload) type Table = [(Address,Port)]
update_table1::Table -> Pkg -> Table update_table1 [] (t,d,y) = [(t,d,y)]
Error is
Type error in explicitly typed binding *** Term : update_table1 *** Type : Table -> Pkg -> [(Pkgtype,Int,Payload)] *** Does not match : Table -> Pkg -> Table
Please kindly suggest, thanks in advance.
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