That's because you still have "Just a" values. Try mapMaybe from Data.Maybe
instead.
On mobile; please excuse any tpyos.
On Thu, 3 Jan. 2019, 1:29 pm Damien Mattei i repost because it seems that the first post of the year in haskell cafe
ailing list has been lost! i cant't see in the archive of january neither
december....
so here it is again: On Tue, Jan 1, 2019 at 10:25 AM Damien Mattei i had filtered a [Maybe Text] type to remove Nothing from the list and
now i want to put the result in a [Text] type but the compiler complains
about the incompatible type : (bd_rows_WDS :: [Only (Maybe Text)]) <- query conn qry_head_WDS (Only
(name::String)) -- remove the records having N°BD NULL
let fltWDS :: [Only Text] = Prelude.filter (\(Only a) ->
case a of
Nothing -> False
Just a -> True)
bd_rows_WDS Prelude> :load UpdateSidonie
[1 of 1] Compiling Main ( UpdateSidonie.hs, interpreted ) UpdateSidonie.hs:282:33: error:
• Couldn't match type ‘Maybe Text’ with ‘Text’
Expected type: [Only Text]
Actual type: [Only (Maybe Text)]
• In the expression:
Prelude.filter
(\ (Only a)
-> case a of
Nothing -> False
Just a -> True)
bd_rows_WDS
In a pattern binding:
fltWDS :: [Only Text]
= Prelude.filter
(\ (Only a)
-> case a of
Nothing -> False
Just a -> True)
bd_rows_WDS
In the expression:
do conn <- connect
defaultConnectInfo
{connectHost = "moita", connectUser = "mattei",
connectPassword = "sidonie2", connectDatabase =
"sidonie"}
(rows :: [(Text, Double)]) <- query_
conn
"SELECT Nom,distance FROM
AngularDistance WHERE distance > 0.000278"
(names :: [Only Text]) <- query_
conn
"SELECT Nom FROM AngularDistance
WHERE distance > 0.000278"
let resLstNames = Prelude.map fromOnly names
....
|
282 | let fltWDS :: [Only Text] = Prelude.filter (\(Only a) ->
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^...
Failed, no modules loaded. how can id do the type conversion,now i'm sure there is no more Nothing
values? _______________________________________________
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