Picture for a moment that the Square-Brackets of the List are Walls.
List in Elm is a close relative to JavaScript’s Array, it’s a collection of values (surrounded by the same literal brackets [] ) and a function can be applied to each item with the List.map function.
Imagine also that the function we want to apply […] can’t reach over the wall!
We use map to “lift” the function over the wall of the List to reach the values inside. The wall is still intact after but the values are now changed.
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MACMURRAY, Andrew, 2019. Map in Elm. post 
maintains nesting through the availability of open doors that permit access to deeper rooms. Explicitly the outermost door leads outside.
What Ward did is …