Slices in Elm

module Main exposing (main)

import Html exposing (Html, div, text)
import Array exposing (Array)


main : Html msg
main =
    div []
        [ demonstrateSlices
        ]


demonstrateSlices : Html msg
demonstrateSlices =
    let
        -- Unlike arrays, Lists in Elm are typed only by the
        -- elements they contain (not the number of elements).
        -- An empty list is represented as [].
        emptyList : List String
        emptyList =
            []

        -- To create a list with initial values, we can use the following syntax
        initialList : List String
        initialList =
            [ "a", "b", "c" ]

        -- We can add elements to a list using the (::) operator or (++) for concatenation
        appendedList : List String
        appendedList =
            "d" :: "e" :: "f" :: initialList

        -- Lists can be copied using the (++) operator
        copiedList : List String
        copiedList =
            initialList ++ []

        -- Slicing in Elm is done using List.take and List.drop
        slicedList1 : List String
        slicedList1 =
            List.drop 2 (List.take 5 appendedList)

        slicedList2 : List String
        slicedList2 =
            List.take 5 appendedList

        slicedList3 : List String
        slicedList3 =
            List.drop 2 appendedList

        -- We can declare and initialize a list in a single line
        declaredList : List String
        declaredList =
            [ "g", "h", "i" ]

        -- For comparing lists, we can use the (==) operator
        listsEqual : Bool
        listsEqual =
            declaredList == [ "g", "h", "i" ]

        -- In Elm, we use List of Lists for multi-dimensional data structures
        twoDList : List (List Int)
        twoDList =
            [ [ 0 ]
            , [ 1, 2 ]
            , [ 2, 3, 4 ]
            ]
    in
    div []
        [ text ("Empty: " ++ Debug.toString emptyList)
        , text ("Initial: " ++ Debug.toString initialList)
        , text ("Appended: " ++ Debug.toString appendedList)
        , text ("Copied: " ++ Debug.toString copiedList)
        , text ("Sliced 1: " ++ Debug.toString slicedList1)
        , text ("Sliced 2: " ++ Debug.toString slicedList2)
        , text ("Sliced 3: " ++ Debug.toString slicedList3)
        , text ("Declared: " ++ Debug.toString declaredList)
        , text ("Lists Equal: " ++ Debug.toString listsEqual)
        , text ("2D List: " ++ Debug.toString twoDList)
        ]

In Elm, we don’t have slices as a separate data type. Instead, we use Lists, which are similar to slices in many ways. Here’s an explanation of the key differences and similarities:

Lists in Elm are immutable, unlike slices in Go which can be modified.
Elm doesn’t have a built-in append function, but we can use the (::) operator to add elements to the front of a list, or (++) to concatenate lists.
Slicing in Elm is done using List.take and List.drop functions, which are similar to slice operations in Go.
Elm doesn’t have a built-in copy function for lists, but we can achieve the same result by concatenating with an empty list.
Multi-dimensional data structures in Elm are represented as Lists of Lists.
Elm uses pattern matching and recursion for many operations that might use loops in Go.

This example demonstrates the basic operations on Lists in Elm, which are analogous to slice operations in Go. The Debug.toString function is used to convert the results to strings for display.

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Slices in Elm