.. default-domain:: chpl .. module:: Set :synopsis: This module contains the implementation of Chapel's standard 'set' type. Set === **Usage** .. code-block:: chapel use Set; or .. code-block:: chapel import Set; This module contains the implementation of Chapel's standard 'set' type. A set is a collection of unique elements. Sets are unordered and unindexed. The highly parallel nature of Chapel means that great care should be taken when performing operations that may invalidate references to set elements. Adding or removing an element from a set may invalidate references to elements contained in the set. All references to set elements are invalidated when the set is cleared or deinitialized. Sets are not parallel safe by default, but can be made parallel safe by setting the param formal 'parSafe` to true in any set constructor. When constructed from another set, the new set will inherit the parallel safety mode of its originating set. When using set operators (e.g., ``A | B``), if both sets contain elements that are ``==`` equivalent, the element from the first argument of the operation will always be chosen for the resultant set. This may happen if the ``==`` operator has been overloaded on the set element type, causing values of the set type to be ``==`` equivalent, even when there may be differences between the elements of the first argument and the elements of the second argument. .. record:: set : serializable A set is a collection of unique elements. Attempting to add a duplicate element to a set has no effect. The set type supports a test for membership via the :proc:`contains` method, along with free functions for calculating the union, difference, intersection, and symmetric difference of two sets. The set type also defines the (proper) subset and (proper) superset operations by overloading common comparison operators. Sets can be iterated over. The set type makes no guarantee of a consistent iteration order. A set can be default initialized (containing no elements), or it may be initialized with elements that are copies of those contained by any type that supports an iterator. The set type is not parallel safe by default. For situations in which such protections are desirable, parallel safety can be enabled by setting `parSafe = true` in any set constructor. A set constructed from another set inherits the parallel safety mode of that set by default. Note that the ``parSafe`` mode is currently unstable and will eventually be replaced by a standalone parallel-safe set type. .. attribute:: type eltType The type of the elements contained in this set. .. attribute:: param parSafe = false .. warning:: 'set.parSafe' is unstable and is expected to be replaced by a separate set type in the future If `true`, this set will perform parallel safe operations. .. attribute:: const resizeThreshold = defaultHashTableResizeThreshold Fractional value that specifies how full this map can be before requesting additional memory. The default value of 0.5 means that the map will not resize until the map is more than 50% full. The acceptable values for this argument are between 0 and 1, exclusive, meaning (0,1). This is useful when you would like to reduce memory impact or potentially speed up how fast the map finds a slot. To override the default value of 0.5, the `defaultHashTableResizeThreshold` config flag can be set at runtime. Note that this default affects all hash-based data structures, including associative domains and maps. .. method:: proc init(type eltType, resizeThreshold = defaultHashTableResizeThreshold, initialCapacity = 16) Initializes an empty set containing elements of the given type. :arg eltType: The type of the elements of this set. :arg resizeThreshold: Fractional value that specifies how full this map can be before requesting additional memory. :arg initialCapacity: Integer value that specifies starting map size. The map can hold at least this many values before attempting to resize. .. method:: proc init(type eltType, param parSafe, resizeThreshold = defaultHashTableResizeThreshold, initialCapacity = 16) .. warning:: 'set.parSafe' is unstable and is expected to be replaced by a separate set type in the future .. method:: proc init(type eltType, iterable, resizeThreshold = defaultHashTableResizeThreshold, initialCapacity = 16) where canResolveMethod(iterable, "these") Initialize this set with a unique copy of each element contained in `iterable`. If an element from `iterable` is already contained in this set, it will not be added again. The formal `iterable` must be a type with an iterator named "these" defined for it. :arg eltType: The type of the elements of this set. :arg iterable: A collection of elements to add to this set. :arg resizeThreshold: Fractional value that specifies how full this map can be before requesting additional memory. :arg initialCapacity: Integer value that specifies starting map size. The map can hold at least this many values before attempting to resize. .. method:: proc init(type eltType, iterable, param parSafe, resizeThreshold = defaultHashTableResizeThreshold, initialCapacity = 16) where canResolveMethod(iterable, "these") .. warning:: 'set.parSafe' is unstable and is expected to be replaced by a separate set type in the future .. method:: proc init=(const ref other: set(?t, ?p)) Initialize this set with a copy of each of the elements contained in the set `other`. This set will inherit the `parSafe` value of the set `other`. :arg other: A set to initialize this set with. .. method:: proc ref add(in element: eltType) Add a copy of the element `element` to this set. Does nothing if this set already contains an element equal to the value of `element`. :arg element: The element to add to this set. .. method:: proc contains(const ref element: eltType): bool Returns `true` if the given element is a member of this set, and `false` otherwise. :arg element: The element to test for membership. :return: Whether or not the given element is a member of this set. :rtype: `bool` .. method:: proc isDisjoint(const ref other: set(eltType, ?)): bool Returns `true` if this set shares no elements in common with the set `other`, and `false` otherwise. .. warning:: `other` must not be modified during this call. :arg other: The set to compare against. :return: Whether or not this set and `other` are disjoint. :rtype: `bool` .. method:: proc ref remove(const ref element: eltType): bool Attempt to remove the item from this set with a value equal to `element`. If an element equal to `element` was removed from this set, return `true`, else return `false` if no such value was found. .. warning:: Removing an element from this set may invalidate existing references to the elements contained in this set. :arg element: The element to remove. :return: Whether or not an element equal to `element` was removed. :rtype: `bool` .. method:: proc ref clear() Clear the contents of this set. .. warning:: Clearing the contents of this set will invalidate all existing references to the elements contained in this set. .. itermethod:: iter these() const ref Iterate over the elements of this set. Yields constant references that cannot be modified. .. warning:: Modifying this set while iterating over it may invalidate the references returned by an iterator and is considered undefined behavior. :yields: A constant reference to an element in this set. .. method:: proc serialize(writer: fileWriter(?), ref serializer) throws Write the contents of this set to a fileWriter. :arg writer: A fileWriter to write to. :arg serializer: The serializer to use when writing. .. method:: proc isEmpty(): bool Returns `true` if this set contains zero elements. :return: `true` if this set is empty. :rtype: `bool` .. method:: proc size The current number of elements contained in this set. .. method:: proc toArray(): [] eltType Returns a new DefaultRectangular array containing a copy of each of the elements contained in this set. The elements of the returned array are not guaranteed to follow any particular ordering. :return: An array containing a copy of each of the elements in this set. :rtype: `[] eltType` .. method:: operator set. = (ref lhs: set(?t, ?), const ref rhs: set(t, ?)) Clear the contents of the set `lhs`, then iterate through the contents of `rhs` and add a copy of each element to `lhs`. .. warning:: This will invalidate any references to elements previously contained in the set `lhs`. :arg lhs: The set to assign to. :arg rhs: The set to assign from. .. method:: operator set.|(const ref a: set(?t, ?), const ref b: set(t, ?)) Return a new set that contains the union of two sets. :arg a: A set to take the union of. :arg b: A set to take the union of. :return: A new set containing the union between `a` and `b`. .. method:: operator set.|=(ref lhs: set(?t, ?), const ref rhs: set(t, ?)) Add to the set `lhs` all the elements of `rhs`. :arg lhs: A set to take the union of and then assign to. :arg rhs: A set to take the union of. .. method:: operator set.+(const ref a: set(?t, ?), const ref b: set(t, ?)) Return a new set that contains the union of two sets. Alias for the `|` operator. :arg a: A set to take the union of. :arg b: A set to take the union of. :return: A new set containing the union between `a` and `b`. .. method:: operator set.+=(ref lhs: set(?t, ?), const ref rhs: set(t, ?)) Add to the set `lhs` all the elements of `rhs`. :arg lhs: A set to take the union of and then assign to. :arg rhs: A set to take the union of. .. method:: operator set.-(const ref a: set(?t, ?), const ref b: set(t, ?)) Return a new set that contains the difference of two sets. :arg a: A set to take the difference of. :arg b: A set to take the difference of. :return: A new set containing the difference between `a` and `b`. .. method:: operator set.-=(ref lhs: set(?t, ?), const ref rhs: set(t, ?)) Remove from the set `lhs` the elements of `rhs`. .. warning:: This will invalidate any references to elements previously contained in the set `lhs`. :arg lhs: A set to take the difference of and then assign to. :arg rhs: A set to take the difference of. .. method:: operator set.&(const ref a: set(?t, ?), const ref b: set(t, ?)) Return a new set that contains the intersection of two sets. :arg a: A set to take the intersection of. :arg b: A set to take the intersection of. :return: A new set containing the intersection of `a` and `b`. .. method:: operator set.&=(ref lhs: set(?t, ?), const ref rhs: set(t, ?)) Assign to the set `lhs` the set that is the intersection of `lhs` and `rhs`. .. warning:: This will invalidate any references to elements previously contained in the set `lhs`. :arg lhs: A set to take the intersection of and then assign to. :arg rhs: A set to take the intersection of. .. method:: operator set.^(const ref a: set(?t, ?), const ref b: set(t, ?)) Return the symmetric difference of two sets. :arg a: A set to take the symmetric difference of. :arg b: A set to take the symmetric difference of. :return: A new set containing the symmetric difference of `a` and `b`. .. method:: operator set.^=(ref lhs: set(?t, ?), const ref rhs: set(t, ?)) Assign to the set `lhs` the set that is the symmetric difference of `lhs` and `rhs`. .. warning:: This will invalidate any references to elements previously contained in the set `lhs`. :arg lhs: A set to take the symmetric difference of and then assign to. :arg rhs: A set to take the symmetric difference of. .. method:: operator set.==(const ref a: set(?t, ?), const ref b: set(t, ?)): bool Return `true` if the sets `a` and `b` are equal. That is, they are the same size and contain the same elements. :arg a: A set to compare. :arg b: A set to compare. :return: `true` if two sets are equal. :rtype: `bool` .. method:: operator set.!=(const ref a: set(?t, ?), const ref b: set(t, ?)): bool Return `true` if the sets `a` and `b` are not equal. :arg a: A set to compare. :arg b: A set to compare. :return: `true` if two sets are not equal. :rtype: `bool` .. method:: operator set.<(const ref a: set(?t, ?), const ref b: set(t, ?)): bool Return `true` if `a` is a proper subset of `b`. :arg a: A set to compare. :arg b: A set to compare. :return: `true` if `a` is a proper subset of `b`. :rtype: `bool` .. method:: operator set.<=(const ref a: set(?t, ?), const ref b: set(t, ?)): bool Return `true` if `a` is a subset of `b`. :arg a: A set to compare. :arg b: A set to compare. :return: `true` if `a` is a subset of `b`. :rtype: `bool` .. method:: operator set.>(const ref a: set(?t, ?), const ref b: set(t, ?)): bool Return `true` if `a` is a proper superset of `b`. :arg a: A set to compare. :arg b: A set to compare. :return: `true` if `a` is a proper superset of `b`. :rtype: `bool` .. method:: operator set.>=(const ref a: set(?t, ?), const ref b: set(t, ?)): bool Return `true` if `a` is a superset of `b`. :arg a: A set to compare. :arg b: A set to compare. :return: `true` if `a` is a superset of `b`. :rtype: `bool`