dhall-1.4.2: Prelude/Text/concatSep

{-
Concatenate a `List` of `Text` values with a separator in between each value

Examples:

```
./concatSep ", " ["ABC", "DEF", "GHI"] = "ABC, DEF, GHI"

./concatSep ", " ([] : List Text) = ""
```
-}
let concatSep : ∀(separator : Text) → ∀(elements : List Text) → Text
    =   λ(separator : Text)
    →   λ(elements : List Text)
    →   let status
            =   List/fold
                Text
                elements
                < Empty : {} | NonEmpty : Text >
                (   λ(element : Text)
                →   λ(status : < Empty : {} | NonEmpty : Text >)
                →   merge
                    {   Empty
                        =   λ(_ : {})
                        →   < NonEmpty = element
                            | Empty : {}
                            >
                    ,   NonEmpty
                        =   λ(result : Text)
                        →   < NonEmpty = element ++ separator ++ result
                            | Empty : {}
                            >
                    }
                    status : < Empty : {} | NonEmpty : Text >
                )
                < Empty = {=} | NonEmpty : Text >
    in  merge
        { Empty    = λ(_ : {}) → ""
        , NonEmpty = λ(result : Text) → result
        }
        status : Text

in  concatSep