This describes how each line has changed and also contains its value.

Compares general lists.

diff [ 1, 3 ] [ 2, 3 ]
--> [ Removed 1, Added 2, NoChange 3 ]

This will never produce Similar, so you can use never in that branch.

diff a b
    |> List.map
        (\change ->
            case change of
                Diff.Added _ ->
                    1


                Diff.Removed _ ->
                    -1


                Diff.NoChange _ ->
                    0


                Diff.Similar _ _ ever ->
                    never ever
        )

Compares two text. Considers two lines similar if they are equivalent ignoring spaces.

Giving the following text

a =
    """aaa
bbb
ddd"""


b =
    """zzz
aaa
ccc
ddd"""

results in

[ Added "zzz"
, NoChange "aaa"
, Removed "bbb"
, Added "ccc"
, NoChange "ddd"
]

.

Compares general lists. Allows specifying when two elements are similar.

diff (\l r -> if abs (l - r) < 1 then Just () else Nothing) [ 1, 3 ] [ 2, 3 ]
--> [ Similar 1 2 (), NoChange 3 ]

Calculate the diff between two multiline strings.

Options for diffing multiline strings.

Default comparison options.

Ignore leading whitespace when comparing multiline strings.

diffLinesWith (defaultOptions |> ignoreLeadingWhitespace) "a" "  a"
--> [ NoChange "a" ]

Equivalent to equalIf (\a b -> String.trimLeft a == String.trimLeft b).

Configure when to consider two lines equal.

As an example you can use \l r -> String.trim l == String.trim r to ignore whitespace around lines.

Configure when to consider two lines similar.