attrset

Types and functions related to Nix attribute sets.

Types

AttrSet

Represents any attribute set in Nix, containing values of a single type.

pub type AttrSet(value)

Functions

from_array

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pub fn from_array(attrs: Array(#(String, a))) -> AttrSet(a)

Creates an attribute set from an array of #(name, value) pairs.

If there are two attributes with the same name, the first occurrence takes precedence.

from_dict

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pub fn from_dict(dict: Dict(String, a)) -> AttrSet(a)

Creates an attribute set from a dictionary with string keys.

from_list

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pub fn from_list(attrs: List(#(String, a))) -> AttrSet(a)

Creates an attribute set from a list of #(name, value) pairs.

If there are two attributes with the same name, the first occurrence takes precedence.

get

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pub fn get(set: AttrSet(a), attr: String) -> Result(a, Nil)

Gets the value associated with that attribute, if it exists.

intersect

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pub fn intersect(
  first: AttrSet(a),
  with second: AttrSet(b),
) -> AttrSet(a)

Generates an attribute set with all attributes in the first set which have the same name as some attribute in the second set.

map_values

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pub fn map_values(
  in set: AttrSet(a),
  with fun: fn(String, a) -> b,
) -> AttrSet(b)

Updates values in the given attribute set using the output of the given function, which is called with each attribute’s name and value and returns the new value.

merge

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pub fn merge(
  first: AttrSet(a),
  with second: AttrSet(a),
) -> AttrSet(a)

Merges two attribute sets, such that attributes in the second set override those in the first with the same name.

names

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pub fn names(in set: AttrSet(a)) -> Array(String)

Obtains the list of attribute names in the given attribute set. Returns an Array as it uses builtins.attrNames. You can use array.to_list to convert to a List.

Examples

from_list([#("a", 5), #("b", 6)]) |> names
// -> array.from_list(["a", "b"])

new

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pub fn new() -> AttrSet(a)

Creates a new, empty attribute set.

set

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pub fn set(
  set: AttrSet(a),
  at attr: String,
  to value: a,
) -> AttrSet(a)

Updates the value of an attribute in the attribute set, returning the new, updated attribute set.

The original attribute set is NOT changed and is immutable.

size

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pub fn size(set: AttrSet(a)) -> Int

Gets the amount of attributes in the attribute set.

to_array

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pub fn to_array(set: AttrSet(a)) -> Array(#(String, a))

Obtains an array of #(name, value) pairs from an attribute set.

to_dict

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pub fn to_dict(set: AttrSet(a)) -> Dict(String, a)

Converts an attribute set to a dictionary with string keys.

to_list

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pub fn to_list(set: AttrSet(a)) -> List(#(String, a))

Obtains a list of #(name, value) pairs from an attribute set.

values

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pub fn values(in set: AttrSet(a)) -> Array(a)

Obtains the list of values in the given attribute set. Returns an Array as it uses builtins.attrValues. You can use array.to_list to convert to a List.

Examples

from_list([#("a", 5), #("b", 6)]) |> values
// -> array.from_list([5, 6])