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Set operators

@> {'you', 'them', 'and', 'me'} with 'or' without 'you'

with and without​

set with elem returns a new set containing all the elements of set plus elem. set without elem returns a new set containing all the elements of set except elem (a no-op if elem isn't a member).

@> {1, 2, 3} with 4
@> {1, 2, 3} without 2
@> {1, 2, 3} without 5   # elem not present: returns set unchanged

Because arrays, strings, byte arrays and dictionaries are just sets of tuples under the hood, with/without work on their underlying (@:, @item:), (@:, @char:), (@:, @byte:) and (@:, @value:) tuples too:

@> [1, 2, 3] without (@: 0, @item: 1)

count and single​

The postfix count operator returns the number of elements in a set:

@> {1, 2, 3} count

The postfix single operator returns the sole element of a one-element set, and fails if the set is empty or has more than one element:

@> {42} single
@> {} single       # FAIL: empty set
@> {1, 2} single   # FAIL: too many elements

Boolean set operators​

Arr.ai supports the conventional set operators.

@> {1, 2, 3} & {2, 3, 4}   # Intersection
@> {1, 2, 3} | {2, 3, 4}   # Union
@> {1, 2, 3} &~ {2, 3, 4}  # Difference
@> {1, 2, 3} ~~ {2, 3, 4}  # Symmetric difference

Power set: ^set​

The power set of a set is the set of all subsets of that set, including the set itself and the empty set.

@> ^{1}
@> ^{1, 2}
@> ^{1, 2, 3}