Sets

Keep only one of each value

Sets use the {| sigil. Repeated entries collapse to one member.

Runnable RiXRun cell

choices := {| 1, 2, 2, 3 |} choices

The result contains each value once. That makes sets a strong fit for membership and combination questions.

Unlike an array, a set does not promise meaningful order or preserve duplicates. Choose it when the question is “which distinct values occur?” rather than “in what sequence did values occur?” Has answers membership directly, and Values converts the members when a later operation specifically needs a traversable sequence.

Combine two sets

Union returns all unique values from both inputs.

Runnable RiXRun cell

warm := {| 1, 2 |} cool := {| 2, 3 |} warm.Union(cool)

Union keeps values present in either set. Intersection keeps only values present in both, while difference keeps values from the receiver that are absent from the other set.

Runnable RiXRun cell

required := {| "read", "write", "share" |} granted := {| "read", "share", "admin" |} {: required.Intersect(granted), required.Diff(granted) }

Read the direction of Diff carefully: the example reports required permissions that are not granted. Reversing receiver and argument instead reports granted permissions that were not requested.

Prefer returned sets

Add, Remove, Union, Intersect, and Diff return new sets. Their bang counterparts update a mutable receiver. Returned sets make comparisons clearer because both “before” and “after” remain available.

Runnable RiXRun cell

original := {| 2, 3, 5 |} extended := original.Add(7) {: original, extended, extended.Has(7) }

Exact numeric equality governs membership, so equivalent rational spellings denote the same set member. The function chips below link the central set operations to their API descriptions and examples.