erlang sets

MODULE

sets

MODULE SUMMARY

Functions for Set Manipulation

DESCRIPTION

Sets are collections of elements with no duplicate elements. The representation of a set is not defined.

This module provides exactly the same interface as the module ordsets but with a defined representation. One difference is that while this module considers two elements as different if they do not match (=:=), ordsets considers two elements as different if and only if they do not compare equal (==).

DATA TYPES

set()

As returned by new/0.

EXPORTS

new() -> set()

Returns a new empty set.

is_set(Set) -> boolean()

Types:

Set = term()

Returns true if Set is a set of elements, otherwise false.

size(Set) -> integer() >= 0

Types:

Set = set()

Returns the number of elements in Set.

to_list(Set) -> List

Types:

Set = set()

List = [term()]

Returns the elements of Set as a list.

from_list(List) -> Set

Types:

List = [term()]

Set = set()

Returns an set of the elements in List.

is_element(Element, Set) -> boolean()

Types:

Element = term()

Set = set()

Returns true if Element is an element of Set, otherwise false.

add_element(Element, Set1) -> Set2

Types:

Element = term()

Set1 = Set2 = set()

Returns a new set formed from Set1 with Element inserted.

del_element(Element, Set1) -> Set2

Types:

Element = term()

Set1 = Set2 = set()

Returns Set1, but with Element removed.

union(Set1, Set2) -> Set3

Types:

Set1 = Set2 = Set3 = set()

Returns the merged (union) set of Set1 and Set2.

union(SetList) -> Set

Types:

SetList = [set()]

Set = set()

Returns the merged (union) set of the list of sets.

intersection(Set1, Set2) -> Set3    %%intersection  交集 相交；交叉

Types:

Set1 = Set2 = Set3 = set()

Returns the intersection of Set1 and Set2.

intersection(SetList) -> Set 

Types:

SetList = [set(), ...]

Set = set()

Returns the intersection of the non-empty list of sets.

is_disjoint(Set1, Set2) -> boolean()    %%disjoint  adj. 不相交的.

Types:

Set1 = Set2 = set()

Returns true if Set1 and Set2 are disjoint (have no elements in common), and false otherwise.

subtract(Set1, Set2) -> Set3

Types:

Set1 = Set2 = Set3 = set()

Returns only the elements of Set1 which are not also elements of Set2.

is_subset(Set1, Set2) -> boolean()

Types:

Set1 = Set2 = set()

Returns true when every element of Set11 is also a member of Set2, otherwise false.

fold(Function, Acc0, Set) -> Acc1

Types:

Function = fun((E :: term(), AccIn) -> AccOut)

Set = set()

Acc0 = Acc1 = AccIn = AccOut = T

Fold Function over every element in Set returning the final value of the accumulator.

如果表为空,则返回Acc0.对表中的每一个对象Elem调用Function(Elem,AccIn),第一次调用时,AccIn为Acc0,后续的每一次调用,AccIn为上一次调用的返回值，最终返回最后一次调用的结果.与lists:fold/3相似.

%%sets:fold(fun(X,Y)->Y+X end,10,G).

filter(Pred, Set1) -> Set2

Types:

Pred = fun((E :: term()) -> boolean())

Set1 = Set2 = set()

Filter elements in Set1 with boolean function Pred.

 %%sets:filter(fun(X)->X end,G).   

See Also

ordsets(3), gb_sets(3)