List Comprehension (For Expression)

List comprehensions are a combination of mapping, filtering and sorting.

[ e1 | id : t in e2 ]

e2 produces a collection of elements with type t, e1 is an expression that allows transformation of the elements using identifier id.

Filters are also allowed:

[ e1 | id : t in e2 filter ]

Example:

[e.title | e : BlogEntry in b.entries 
           where e.created > date 
           order by e.created desc]

This expression returns all titles (e.title) from b.entries where the time created (e.created) is greater than a certain date, ordered by e.created in descending order. Both the where and order by clauses are optional. An ordering is either ascending (asc) or descending (desc).

Conjunction

And [ e1 | id : t in e2 ]

If e1 produces a boolean, the list comprehension can be preceded by "And" to create the conjunction of the elements produced by the list comprehension.

Disjunction

Or [ e1 | id : t in e2 ]

If e1 produces a boolean, the list comprehension can be preceded by "Or" to create the disjunction of the elements produced by the list comprehension.