List Comprehension

A list comprehension creates a new list by iterating over an existing list, optionally filtering elements and transforming them.

Syntax
<list comprehension> ::=
  "[" <variable> "IN" <list> [ < "WHERE" | "FILTER" > <condition> ] [ "|" <expr> ] "]"

Details

• <variable>: the iteration variable, bound to each element in <list> in turn.
• WHERE|FILTER <condition>: optional filter; only elements that meet the condition are included.
• <expr> transforms each element. If omitted, returns the original element.

Examples

Transform each element:

GQL
RETURN [x IN [1, 2, 3, 4, 5] | x * 10]

Result: [10, 20, 30, 40, 50]

Filter elements:

GQL
RETURN [x IN [1, 2, 3, 4, 5] WHERE x > 2]

Result: [3, 4, 5]

Filter and transform:

GQL
RETURN [x IN [1, 2, 3, 4, 5] WHERE x > 2 | x * 10]

Result: [30, 40, 50]