`let … in` statement

The statement let <VAR> in <EXPRESSION> assigns the results of a stream valued expression <EXPRESSION> to the variable <VAR>, one at a time.

The expression can only be a call to a function that returns a stream of answers.

If each tuple in the stream contains more than one value, multiple variables must be specified of the left hand side of the assignment.

Schema for the following examples

#!test[schema, commit]
define
entity person;
entity company;
# Dummy definition
fun past-employments($person: person) -> { integer, company }:
match
  let $year = 2000;
  $company isa company;
return {$year, $company};

#!test[read]
let $year, $company in past-employments($person);