I have a complex data structure and I had to create this short example for better understanding.
type alias People =
{ name : String
, sex : String
, phones : List Phone
}
type alias Phone =
{ number : String
, isActive : Bool
}
This structure populated:
people = [
{ name = "_me"
, sex = "M"
, phones = [
{ number = "(99) 99 9 9999-9999"
, isActive = True
}]
},
{ name = "_you"
, sex = "M"
, phones = [
{ number = "(11) 11 1 1111-1111"
, isActive = True
},
{ number = "(22) 22 2 2222-2222"
, isActive = False
}]
}]
And I would like to get only the 'phones' from the 'people' list, as in the example below
phones = [
{ number = "(99) 99 9 9999-9999"
, isActive = True
},
{ number = "(11) 11 1 1111-1111"
, isActive = True
},
{ number = "(22) 22 2 2222-2222"
, isActive = False
}]
I've been trying for 3 days, but to no avail.
You can pull out all the phone numbers into a list by mapping over to get the phone number list of a person, then concatenating those phone number lists together:
getPhones : List People -> List Phone
getPhones = List.concat << List.map .phones
Related
I have the following initialModel,
initialModel : Model
initialModel =
{ cards =
[ { url = "Gita.jpg", card = 1, selected = False }
, { url = "Kali.jpg", card = 2, selected = False }
, { url = "Arjuna.jpg", card = 3, selected = False }
, { url = "Krishna.jpg", card = 4, selected = False }
, { url = "Manjusri.jpg", card = 5, selected = False }
, { url = "siddartha.jpg", card = 6, selected = False }
, { url = "bodhidharma2.jpg", card = 7, selected = False }
]
, selectedCards = [ "card1" ]
, activeCard = ""
}
And I have them hooked with onClick,
type Msg
= ClickedCard { url : String, id : String }
| Other
update : Msg -> Model -> Model
update msg model =
case msg of
ClickedCard data ->
{ model
| activeCard = data.id
, selectedCards = selectedCards ++ data.id -- This line is pseudo-code
}
_ ->
model
How can I make that update work? So, in the end, every click on a new card should make it on the selectedCards list.
games =
[ { id = 1
, points =
[ { player_id = 1, score = 20 }
, { player_id = 2, score = 10 }
, { player_id = 3, score = 0 }
]
}
, { id = 2
, points =
[ { player_id = 1, score = 20 }
, { player_id = 2, score = 5 }
, { player_id = 3, score = 0 }
]
}
, { id = 3
, points =
[ { player_id = 1, score = 20 }
, { player_id = 2, score = 5 }
, { player_id = 3, score = 10 }
]
}
]
I have a list of 'games' records which each have a list of points for each player.
Is it possible to fold each score of each player across each game to display a 'total'.
Something like:
[ { player_id = 1, score = 60 }
, { player_id = 2, score = 20 }
, { player_id = 3, score = 10 }
]
Thanks in advance.
You need a double fold, where the key code is
main : Html msg
main =
let
go { points } acc =
let
goInner { player_id, score } accInner =
Dict.update player_id (updater score) accInner
in
List.foldl goInner acc points
in
List.foldl go Dict.empty games
|> toString
|> text
updater : Int -> Maybe Int -> Maybe Int
updater score existingVal =
existingVal
|> Maybe.withDefault 0
|> (+) score
|> Just
See [https://ellie-app.com/gq8VFfS8Ja1/0](this ellie)
This gets you the answer you want albeit in a slightly different format
I want to update my model this way:
updatedModel =
if model.firstChord && model.secondChord then
{ model | firstChord = {}, secondChord = {} }
else
model
the firstChord and the secondChord both are of the type Chord:
type alias Chord =
{ root : Maybe Pitch
, third : Maybe Pitch
, fifth : Maybe Pitch
}
The pitch type looks like:
-- pitch
type alias Pitch = ( PitchName, PitchLevel )
-- pitch name
type alias PitchName = String
-- pitch level
type alias PitchLevel = Int
My initial Model has these fields:
{ firstChord =
{ root = ( "C", 3 )
, third = ( "E", 3 )
, fifth = ( "G", 3 )
}
, secondChord =
{ root = ( "F", 3 )
, third = ( "A", 3 )
, fifth = ( "C", 4 )
}
I like to have optional pitch values.
How can I update my model giving it a value OR nothing?
Thanks.
Not quite sure what are you looking for. I guest you would like to have a Maybe Chord like this.
type Pitch =
Pitch String Int
type alias Chord =
{ root: Maybe Pitch
, third: Maybe Pitch
, fifth: Maybe Pitch
}
type alias Model =
{ firstChord: Maybe Chord
, secondChord: Maybe Chord
}
init: Model
init =
{ firstChord =
{ root = Pitch "C" 3
, third = Pitch "E" 3
, fifth = Pitch "G" 3
}
, secondChord =
{ root = Pitch "F" 3
, third = Pitch "A" 3
, fifth = Pitch "C" 4
}
}
update: Model -> Model
update model =
case (model.firstChord, model.secondChord) of
(Just first, Just second) ->
{ model | firstChord = Nothing, secondChord = Nothing}
_ ->
model
When you have a Maybe a type, such as Maybe Pitch you have two ways to set its value: Nothing or Just a. So instead of this:
{ firstChord =
{ root = ( "C", 3 )
, third = ( "E", 3 )
, fifth = ( "G", 3 )
}
, secondChord =
{ root = ( "F", 3 )
, third = ( "A", 3 )
, fifth = ( "C", 4 )
}
...you need to do this:
{ firstChord =
{ root = Just ( "C", 3 )
, third = Just ( "E", 3 )
, fifth = Just ( "G", 3 )
}
, secondChord =
{ root = Just ( "F", 3 )
, third = Just ( "A", 3 )
, fifth = Just ( "C", 4 )
}
Of course, you then use Nothing so indicate no value:
firstChord =
{ root = Just ( "C", 3 )
, third = Just ( "E", 3 )
, fifth = Nothing
}
(edit) i'm using F# interactive in Xamarin 6.3 on MacOS Sierra and Deedle 1.2.5 together with FsLab –
I'm trying this code taken from http://bluemountaincapital.github.io/Deedle/frame.html
and this produces an error.
type Person =
{ Name:string; Age:int; Countries:string list; }
let peopleRecds =
[ { Name = "Joe"; Age = 51; Countries = [ "UK"; "US"; "UK"] }
{ Name = "Tomas"; Age = 28; Countries = [ "CZ"; "UK"; "US"; "CZ" ] }
{ Name = "Eve"; Age = 2; Countries = [ "FR" ] }
{ Name = "Suzanne"; Age = 15; Countries = [ "US" ] } ]
// Turn the list of records into data frame
let peopleList = Frame.ofRecords peopleRecds
// Use the 'Name' column as a key (of type string)
let people = peopleList |> Frame.indexRowsString "Name"
people?Age;;
val it : Series<string,float> =
Joe -> 51
Tomas -> 28
Eve -> 2
Suzanne -> 15
people.Columns?Age.TryAs<string>();;
Stopped due to error System.Exception: Operation could not be
completed due to earlier error Lookup on object of indeterminate type
based on information prior to this program point. A type annotation
may be
(
{
iReplyId = 3870;
name = rahul;
},
{
iReplyId = 3914;
name = Tom;
},
{
iReplyId = 3873;
name = Smith;
},
{
iReplyId = 3871;
name = yator;
},
{
iReplyId = 3872;
name = jack;
},
{
iReplyId = 3875;
name = smith;
},
{
iReplyId = 3876;
name = rancho;
},
{
iReplyId = 3878;
name = vid;
},
)
My requirement is to filter this array with multiple condtion like iReplyId = 3871,3870,3914 by using nspredicate. i tried so much but but i didn't get the solution with predicate, i can solve this by using for loop but that is not a good way.
Any help is highly appreciated.
[array filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"iReplyId IN (%#)",[idsArray componentsJoinedByString:#","]]]