"There are several implementations of sets in the Factor library. More can be added if they implement the words of the set protocol, the basic set operations."
{ $subsections
"sequence-sets"
"hash-sets"
"bit-sets"
} ;
ARTICLE: "sequence-sets""Sequences as sets"
"Any sequence can be used as a set. The members of this set are the elements of the sequence. Calling the word " { $link members } " on a sequence returns a copy of the sequence with only one listing of each member. Destructive operations " { $link adjoin } " and " { $link delete } " only work properly on growable sequences like " { $link vector } "s."
"Care must be taken in writing efficient code using sequence sets. Testing for membership with " { $link in? } ", as well as the destructive set operations, take time proportional to the size of the sequence. Another representation, like " { $link "hash-sets" } ", would take constant time for membership tests. But binary operations like " { $link union } " are asymptotically optimal, taking time proportional to the sum of the size of the inputs."
{ $class-description "The class of all sets. Custom implementations of the set protocol should be declared as instances of this mixin for all set implementation to work correctly." } ;
{ $description "Destructively adds " { $snippet "elt" } " to " { $snippet "set" } ". For sequences, this guarantees that this element is not duplicated, and that it is at the end of the sequence." $nl "Each mutable set type is expected to implement a method on this generic word." }
{ $description "Destructively removes " { $snippet "elt" } " from " { $snippet "set" } ". If the element is not present, this does nothing." $nl "Each mutable set type is expected to implement a method on this generic word." }
{ $description "Creates a sequence with a single copy of each member of the set." $nl "Each set type is expected to implement a method on this generic word." } ;
{ $description "Tests whether the element is a member of the set." $nl "Each set type is expected to implement a method on this generic word as part of the set protocol." } ;
{ $description "Outputs a set consisting of elements present in " { $snippet "set1" } " but not " { $snippet "set2" } ", comparing elements for equality." $nl "This word has a default definition which works for all sets, but set implementations may override the default for efficiency."
{ $description "Outputs the intersection of all the sets of the sequence " { $snippet "sets" } ", or " { $link f } " if " { $snippet "sets" } " is empty." } ;
{ $description "Outputs a set consisting of elements present in either " { $snippet "set1" } " or " { $snippet "set2" } " which does not contain duplicate values." $nl "This word has a default definition which works for all sets, but set implementations may override the default for efficiency." }
{ $description "If the conversion is defined for the exemplar, converts the set into a set of the exemplar's class. This is not guaranteed to create a new set, for example if the input set and exemplar are of the same class." $nl "Set implementations may optionally implement a method on this generic word. The default implementation returns its input set." }
{ $description "Returns the subsequence of the given sequence consisting of members of the set. This may contain duplicates, if the sequence has duplicates." } ;
{ $description "Returns the subsequence of the given sequence consisting of things that are not members of the set. This may contain duplicates, if the sequence has duplicates." } ;
