Some operators allow specifying particular sequences of calls (scripts) that will be executed inside the scope of the operator itself. We name those as subscripts.
That is the case for the
Array<T>::map<0>(subscript: (item: T) => O)
operator, which applies a subscript in parallel on every
T item found
in the input
Array<T> and then collects the results of the
(item: T)=> 0 subscripts into a single
Array<O> that commits to have the same
number of items as the input
Therefore, the first call in a subscript must be compatible with the type of the input.