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List (Cons-based) ​

Experimental API

You are viewing the documentation for an experimental API. Experimental APIs may have potential or known issues, and may be removed or changed at any time. Use caution when implementing in a production environment.

The List in this section specifically refers to the Cons List commonly defined in most functional programming languages, as opposed to the Array-based List defined in another section of this library.

Undeniably, this is a logically perfect Cons List, making full use of the yield syntax provided by the JavaScript language. It supports many nested Lazy operations or infinite lists. Due to the nature of the Cons List, we completed it in a very short time. However, it currently cannot hold too many elements, which is why it is in the experimental section.

L.lazy() ​

Generates a List based on any iterable object.

  • Type
  • Details

Takes an iterable object as an argument and transforms it into a Cons List.

  • Example
js
L.lazy([1, 1, 4, 5, 1, 4]); //List [1, 1, 4, 5, 1, 4]
L.lazy([1, 1, 4, 5, 1, 4]); //List [1, 1, 4, 5, 1, 4]

L.seq() ​

Converts a List back into an Array.

  • Type
  • Details

Takes a list as an argument and transforms it back into an array.

  • Example
js
L.seq(L.lazy([1, 1, 4, 5, 1, 4])); // [1, 1, 4, 5, 1, 4]
L.seq(L.lazy([1, 1, 4, 5, 1, 4])); // [1, 1, 4, 5, 1, 4]

Gets the first element of a List.

  • Type
  • Details

Takes a list as an argument and returns its first element.

  • Example
js
L.head(L.lazy([1, 1, 4, 5, 1, 4])); // 1
L.head(L.lazy([1, 1, 4, 5, 1, 4])); // 1

L.isEmpty() ​

Determines whether a List is empty.

  • Type
  • Details

Takes a list as an argument and determines whether it is empty.

  • Example
js
L.isEmpty(L.lazy([])); // true
L.isEmpty(L.lazy([])); // true

L.iter() ​

Generates an iterable object for a List.

  • Type
  • Details

Takes a list as an argument and returns an iterable object that corresponds to that list.

  • Example
js
const myList = L.lazy([1, 2, 3, 4, 5]);
for (const x of L.iter(myList)) console.log(x); //1 2 3 4 5
const myList = L.lazy([1, 2, 3, 4, 5]);
for (const x of L.iter(myList)) console.log(x); //1 2 3 4 5

L.range() ​

Generates a list based on a range and an iterator function.

  • Type
  • Details

Takes three arguments: the start of the range, the end of the range, and an iterator function. Returns a list that starts from the beginning of the range and iterates to the end of the range based on the iterator function.

  • Example
js
L.range(1, 5, add(1)); // List [1, 2, 3, 4, 5]
L.range(1, 5, add(1)); // List [1, 2, 3, 4, 5]

L.tail() ​

Removes the first element from a List.

  • Type
  • Details

Takes a list as an argument and removes its first element.

  • Example
js
L.tail(L.lazy(1, 2, 3, 4, 5)); // List [2, 3, 4, 5]
L.tail(L.lazy(1, 2, 3, 4, 5)); // List [2, 3, 4, 5]

L.iterate() ​

Returns an infinitely iterating list.

  • Type
  • Details

Takes a function and an initial value as arguments and returns an infinite list that iteratively applies the function to the initial value.

  • Example
js
L.iterate((x) => x * 2, 1); // List [2, 4, 8, 16, 32...]
L.iterate((x) => x * 2, 1); // List [2, 4, 8, 16, 32...]

L.map() ​

Maps over a list.

  • Type
  • Details

Takes a mapping function and a list as arguments, and the entire list will be mapped by the mapping function.

  • Example
js
L.map(
	(x) => x + 1,
	L.iterate((x) => x * 2, 1)
); // List [3, 5, 9, 17, 33...]
L.map(
	(x) => x + 1,
	L.iterate((x) => x * 2, 1)
); // List [3, 5, 9, 17, 33...]

L.flatMap() ​

Maps over a list.

  • Type
  • Details

Takes a mapping function and a list as arguments, and the entire list will be mapped by the mapping function.

The difference between this function and map is that the return value of the argument function should be a list, and this function will automatically flatten it into a single list.

  • Example
js
L.flatMap(
	(x) => L.lazy([x + 1, 1]),
	L.iterate((x) => x * 2, 1)
); // List [3, 1, 5, 1, 9, 1, 17, 1, 33...]
L.flatMap(
	(x) => L.lazy([x + 1, 1]),
	L.iterate((x) => x * 2, 1)
); // List [3, 1, 5, 1, 9, 1, 17, 1, 33...]

L.concat() ​

Concatenates two lists.

  • Type
  • Details

Takes two lists as arguments and concatenates them into a single list.

  • Example
js
L.concat(L.lazy([1, 2, 3]), L.lazy([4, 5, 6]));
// List [1, 2, 3, 4, 5, 6]
L.concat(L.lazy([1, 2, 3]), L.lazy([4, 5, 6]));
// List [1, 2, 3, 4, 5, 6]

L.take() ​

Takes the first elements from a List.

  • Type
  • Details

Takes a positive integer and a list as arguments and returns a list containing the first elements of the given list.

  • Example
js


L.take(2, L.lazy([1, 2, 3])); // List [1, 2]


L.take(2, L.lazy([1, 2, 3])); // List [1, 2]

L.drop() ​

Drops the first elements from a List.

  • Type
  • Details

Takes a positive integer and a list as arguments and returns a list containing all but the first elements of the given list.

  • Example
js
L.drop(2, L.lazy([1, 2, 3])); // List [3]
L.drop(2, L.lazy([1, 2, 3])); // List [3]

L.repeat() ​

Generates an infinite list of constant values.

  • Type
  • Details

Takes a value as an argument and returns an infinite list containing that value.

  • Example
js
L.repeat('Screeps is a amazing game.');
//List ["Screeps is a amazing game.", "Screeps is a amazing game."...]
L.repeat('Screeps is a amazing game.');
//List ["Screeps is a amazing game.", "Screeps is a amazing game."...]

L.filter() ​

Filters elements from a list based on a rule.

  • Type
  • Details

Takes a filtering rule and a list as arguments and returns a list containing the elements that pass the filtering rule.

  • Example
js
L.filter(lte(3), L.lazy([1, 2, 3, 4, 5])); // List [1, 2, 3]
L.filter(lte(3), L.lazy([1, 2, 3, 4, 5])); // List [1, 2, 3]

L.reject() ​

Filters elements from a list based on a rule in reverse.

  • Type
  • Details

Takes a filtering rule and a list as arguments and returns a list containing the elements that do not pass the filtering rule.

  • Example
js
L.reject(lte(3), L.lazy([1, 2, 3, 4, 5])); // List [4, 5]
L.reject(lte(3), L.lazy([1, 2, 3, 4, 5])); // List [4, 5]

L.forEach() ​

Applies a function to each element in a list.

  • Type
  • Details

Takes a function and a list as arguments. Each element in the list will be applied to the function.

  • Example
js
L.forEach((v) => console.log(v), L.lazy([1, 2, 3]));
// 1 2 3 (ignore enter)
L.forEach((v) => console.log(v), L.lazy([1, 2, 3]));
// 1 2 3 (ignore enter)

L.takeWhile() ​

Takes elements from the beginning of the list based on a rule until the rule is not satisfied.

  • Type
  • Details

Takes a rule function and a list as arguments. Returns a list containing the elements taken from the beginning of the list based on the rule until an element is encountered that does not satisfy the rule.

  • Example
js
L.takeWhile(includes('a'), L.lazy(['ab', 'ac', 'bb']));
// List ["ab", "ac"]
L.takeWhile(includes('a'), L.lazy(['ab', 'ac', 'bb']));
// List ["ab", "ac"]

L.dropWhile() ​

Drops elements from the beginning of the list based on a rule until the rule is not satisfied.

  • Type
  • Details

Takes a rule function and a list as arguments. Returns a list containing the remaining elements after dropping the elements from the beginning of the list based on the rule until an element is encountered that does not satisfy the rule.

  • Example
js
L.dropWhile(includes('a'), L.lazy(['ab', 'ac', 'bb']));
// List ["bb"]
L.dropWhile(includes('a'), L.lazy(['ab', 'ac', 'bb']));
// List ["bb"]

L.zipWith() ​

Generates a new list by element-wise processing of two lists.

  • Type
  • Details

Takes a binary function as the first argument, followed by two lists of the same length ().

Returns a new list of the same length as the input lists, where .

  • Example
js
L.zipWith((a, b) => a + b, L.lazy([1, 2, 3]), L.lazy([1, 2, 3]));
// List [2, 4, 6]
L.zipWith((a, b) => a + b, L.lazy([1, 2, 3]), L.lazy([1, 2, 3]));
// List [2, 4, 6]

L.shield() ​

Removes a specific value from a list.

  • Type
  • Details

Takes a value to shield as the first argument, followed by a list. Returns a list without the shielded value.

  • Example
js
L.shield(1, L.lazy([1, 1, 4, 5, 1, 4]));
// List [4, 5, 4]
L.shield(1, L.lazy([1, 1, 4, 5, 1, 4]));
// List [4, 5, 4]

L.choose() ​

Chooses a specific value from a list.

  • Type
  • Details

Takes a value to choose as the first argument, followed by a list. Returns a list containing only the chosen value.

  • Example
js
L.choose(1, L.lazy([1, 1, 4, 5, 1, 4]));
// List [1, 1, 1]
L.choose(1, L.lazy([1, 1, 4, 5, 1, 4]));
// List [1, 1, 1]

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