How can I iterate over the list of records to apply a function

[alexmu...@gmail.com]

Hello,

I am new to elm syntax. I have a list of records with name and age. I want to apply a test function to each record. The function takes one record as input and returns a boolean value. Depending on True or false, I want to take a specific action for each record. How can I implement this in elm? If it was Python, I will just iterate over each item in the list and pass it as a parameter to the function.

[Duane Johnson]

Hi Alex,

Perhaps this helps?

$ elm repl

---- elm-repl 0.17.1 -----------------------------------------------------------

 :help for help, :exit to exit, more at <https://github.com/elm-lang/elm-repl>

--------------------------------------------------------------------------------

> a = [1, 2, 3, 4, 5]

[1,2,3,4,5] : List number

> isOdd n = (n % 2 == 1)

<function:_user$project$Repl$isOdd> : Int -> Bool

> odds = List.filter isOdd a

[1,3,5] : List Int

> doAction n = n + 1

<function:_user$project$Repl$doAction> : number -> number

> List.map doAction odds

[2,4,6] : List Int

Here, I take a list of integers (in your case it would be records) and filter on just the ones I want (in this case, odd numbers). Then I use the `map` function to apply the `doAction` function to each.

On Mon, Dec 26, 2016 at 6:40 AM, <alexmu...@gmail.com> wrote:

Hello,

I am new to elm syntax. I have a list of records with name and age. I want to apply a test function to each record. The function takes one record as input and returns a boolean value. Depending on True or false, I want to take a specific action for each record. How can I implement this in elm? If it was Python, I will just iterate over each item in the list and pass it as a parameter to the function.

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[Aaron VonderHaar]

Hello, the answer depends a bit on what you intend to do with the Bools after you have them...

But if, as you describe, you just want to end up with a List of Bools, then

    List.map (\r -> r.age >= 21) yourRecords

But I expect you may also be interested in one of `List.filter`, `List.all`, or `List.any`.  http://package.elm-lang.org/packages/elm-lang/core/5.0.0/List

On Mon, Dec 26, 2016 at 5:40 AM, <alexmu...@gmail.com> wrote:

Hello,

I am new to elm syntax. I have a list of records with name and age. I want to apply a test function to each record. The function takes one record as input and returns a boolean value. Depending on True or false, I want to take a specific action for each record. How can I implement this in elm? If it was Python, I will just iterate over each item in the list and pass it as a parameter to the function.