Views (parameterized functions that return a relation) and inlining

[julianhyde]

In Morel, a query is an expression, and a function is a parameterized expression. What a database would call a 'view' is, in Morel, just a function that returns a relation.

You can substitute expressions, predicates (lambda expressions that return bool), and even other functions/views into views.

For example, here we define an empsIn view whose parameters are emps (a table) and predicate (a condition to apply to each row):

let
  fun empsIn emps predicate =
    from e in emps
    where predicate e
in
  from e in (empsIn emps (fn e => e.deptno = 30))
  yield e.name
end;
val it = ["Shaggy","Scooby"] : string list

[julianhyde]

Fixed in 5f17ce1.