Collections

len

The number of items in an array or list, characters in text, or entries in a map.

xs (array) -- an array or list

append

Adds an item to the end. Given a name, the array itself grows (like xs.append(v)); a non-number item turns a number array into a list.

xs (array) -- an array or list
item (any) -- the item to add

concat

A new array or list: the first followed by the second.

xs (array) -- first
ys (array) -- second

reverse

A new array or list in reverse order. (On a linked list, reverse animates the in-place reversal -- see Data Structures.)

xs (array) -- an array or list

sort

A new array sorted from smallest to largest, compared exactly (sqrt(2) sorts after 1.4142). Quantities sort by their value in one unit (250 mN before 3 N).

xs (array) -- an array of numbers

contains

Whether an array or list has an item equal to the value, text contains a piece of text, or a map has a key. (On a set, set membership -- see Sets.)

xs (array) -- an array or list
item (any) -- the value to look for

indexOf

The position (from 0) of the first item equal to the value, or -1 if there is none.

xs (array) -- an array or list
item (any) -- the value to look for

keys

A map's keys in the order they were added (a record's field names).

m (map) -- a map or record

values

A map's values in the order their keys were added.

m (map) -- a map or record

has

Whether a map has the key.

m (map) -- a map or record
key (any) -- text, a number or true/false

delete

Removes a key (and its value) from a map, and shows the map.

m (map) -- a map
key (any) -- the key to remove

filter

The items of an array or list for which a condition holds, in their order. The item is called x in the condition, or the name given third. The same as xs[condition], e.g. xs[xs > 20].

xs (array) -- an array or list
condition (expression) -- a condition on the item, e.g. x > 20
name (name) -- optional: the item's name in the condition (default x)

countWhere

How many items of a collection satisfy a condition, or how many tuples, orderings or subsets of its items do. countWhere(xs, condition) counts the items as filter selects them (the item called x, or the name given third); xs may be a whole number n for the numbers 1..n. countWhere(xs, fn(x, y) condition) counts the ordered pairs (triples, ... : one entry per parameter of the function; an item may repeat) for which the function holds; a third argument "distinct" allows no repeated item (the k-permutations), "sets" counts the subsets of that many items (each once, in the list's order), and "permutations" tests every ordering of the whole list, given to a function of one parameter as a list (up to 9 items). Up to a million tuples; the count is exact. For an unordered pair with repeats count sets and singles separately. relationWhere(A, B, rule, x, y) lists the pairs instead of counting them.

xs (array) -- an array or list, or a whole number n for 1..n
condition (expression) -- a condition on the item (x, or the name given third), or an anonymous function fn(x, y) ... of as many parameters as the tuple has entries
mode (string) -- optional: with a function, "tuples" (default: entries may repeat), "distinct", "sets" or "permutations"; with a condition, the item's name (default x)

permutations

Every ordering of the items of a list, as a list of lists (n! of them: up to 9 items). xs may be a whole number n for 1..n. filter and countWhere take the result; countWhere(xs, fn(p) ..., "permutations") counts without listing.

xs (array) -- an array or list, or a whole number n for 1..n

tuples

Every ordered k-tuple of the items of a list, an item allowed to repeat, as a list of lists (n^k of them, up to a million). xs may be a whole number n for 1..n.

xs (array) -- an array or list, or a whole number n for 1..n
k (integer) -- the entries in each tuple

subsets

Every subset of k items of a list, each in the list's order, as a list of lists (nCr(n, k) of them, up to a million). xs may be a whole number n for 1..n. powerSet gives the subsets of every size.

xs (array) -- an array or list, or a whole number n for 1..n
k (integer) -- the items in each subset

slice

The items from position i up to (not including) j, as xs[i:j]; without j, to the end. Positions count from 0; a negative one counts from the end. Text is sliced by character.

xs (array) -- an array, list or text
i (integer) -- the first position
j (integer) -- optional: the position to stop before