Set¶

The Set type has the following methods.

contains¶

Set.contains: (self: Set[T], element: T) -> Bool

Return whether the set contains a given element. For example:

// Evaluates to [true, false].
[for needle in ["a", "z"]: {"a", "b", "c"}.contains(needle)]

except¶

Set.except: (self: Set[T], element: T) -> Set[T]

Return a copy of the set, with the given element omitted. If the element was not present in the first place, then the result is identical to the input.

{1, 2, 3}.except(2)
// Evaluates to:
{1, 3}

filter¶

Set.filter: (self: Set[T], predicate: T -> Bool) -> Set[T]

Construct a new set that contains only the elements where predicate returned true. The result is equivalent to a set comprehension, a and b are identical in this example:

let xs = {1, 2, 3};
let a = xs.filter(x => x > 1);
let b = {
  for x in xs:
  if x > 1:
  x
};
// Both a and b evaluate to:
{2, 3}

Set comprehensions are more general than filter: they support nested loops, and let-bindings are accessible to the inner scope. Still, filter can be useful, especially for iteratively refining a query in an rcl query command.

flat_map¶

Set.flat_map: (self: Set[T], map_element: T -> Set[U]) -> Set[U]

Construct a new set by taking every element in the set, applying map_element to it (which should return a collection), and concatenating those results. flat_map is like map, except that it flattens the result. It is equivalent to a set comprehension with a nested loop: a and b are identical in this example:

let apps = {
  { name = "sshd", ports = {22} },
  { name = "nginx", ports = {80, 443} },
};
let a = apps.flat_map(app => app.ports);
let b = {
  for app in apps:
  for port in app.ports:
  port
};
// Both a and b evaluate to:
{22, 80, 443}

Set comprehensions are often clearer in configuration files, especially when the body is large. They are also more general: set comprehensions support arbitrary nesting, filtering with if, and let-bindings are accessible to the inner scope. Still, flat_map can be useful, especially for iteratively refining a query in an rcl query command.

group_by¶

Set.group_by: (self: Set[T], get_key: T -> U) -> Dict[U, Set[T]]

Group the elements of the set by a key selected by get_key.

let foods = {
  { category = "fruit", name = "apple" },
  { category = "fruit", name = "pear" },
  { category = "vegetable", name = "onion" },
  { category = "vegetable", name = "carrot" },
};
foods.group_by(food => food.category)

// Evaluates to:
{
  fruit = {
    { category = "fruit", name = "apple" },
    { category = "fruit", name = "pear" },
  },
  vegetable = {
    { category = "vegetable", name = "carrot" },
    { category = "vegetable", name = "onion" },
  },
}

key_by¶

Set.key_by: (self: Set[T], get_key: T -> U) -> Dict[U, T]

Build a dictionary with the key selected by get_key as key, and the set elements as values. The keys must be unique. When a key is not unique, this method fails and reports the conflicting values. See also List.key_by for an example.

map¶

Set.map: (self: Set[T], map_element: T -> U) -> Set[U]

Construct a new set by applying map_element to every element in the set. The result is equivalent to a set comprehension, a and b are identical in this example:

let xs = {1, 2, 3};
let a = {for x in xs: x * 2};
let b = xs.map(x => x * 2);
// Both a and b evaluate to:
{2, 4, 6}

Set comprehensions are often clearer in configuration files, especially when the body is large. They are also more general: set comprehensions support nested loops and filtering with if. Still, map can be useful, especially for iteratively refining a query in an rcl query command.

len¶

Set.len: (self: Set[T]) -> Int

Return the number of elements in the set. For example:

// Evaluates to 3.
{1, 1, 2, 2, 3, 3}.len()

sum¶

Set.sum: (self: Set[Int]) -> Int

Return the sum of the elements in the set. For example:

// Evaluates to 42.
{3, 7, 11, 21}.sum()