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A.18.6 The Package Containers.Ordered_Maps

Static Semantics

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The generic library package Containers.Ordered_Maps has the following declaration:

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generic type Key_Type is private; type Element_Type is private; with function "<" (Left, Right : Key_Type) return Boolean is <>; with function "=" (Left, Right : Element_Type) return Boolean is <>; package Ada.Containers.Ordered_Maps is pragma Preelaborate (Ordered_Maps);

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function Equivalent_Keys (Left, Right : Key_Type) return Boolean;

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type Map is tagged private; pragma Preelaborable_Initialization(Map);

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type Cursor is private; pragma Preelaborable_Initialization(Cursor);

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Empty_Map : constant Map;

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No_Element : constant Cursor;

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function "=" (Left, Right : Map) return Boolean;

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function Length (Container : Map) return Count_Type;

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function Is_Empty (Container : Map) return Boolean;

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procedure Clear (Container : in out Map);

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function Key (Position : Cursor) return Key_Type;

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function Element (Position : Cursor) return Element_Type;

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procedure Replace_Element (Container : in out Map; Position : in Cursor; New_Item : in Element_Type);

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procedure Query_Element (Position : in Cursor; Process : not null access procedure (Key : in Key_Type; Element : in Element_Type));

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procedure Update_Element (Container : in out Map; Position : in Cursor; Process : not null access procedure (Key : in Key_Type; Element : in out Element_Type));

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procedure Move (Target : in out Map; Source : in out Map);

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procedure Insert (Container : in out Map; Key : in Key_Type; New_Item : in Element_Type; Position : out Cursor; Inserted : out Boolean);

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procedure Insert (Container : in out Map; Key : in Key_Type; Position : out Cursor; Inserted : out Boolean);

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procedure Insert (Container : in out Map; Key : in Key_Type; New_Item : in Element_Type);

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procedure Include (Container : in out Map; Key : in Key_Type; New_Item : in Element_Type);

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procedure Replace (Container : in out Map; Key : in Key_Type; New_Item : in Element_Type);

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procedure Exclude (Container : in out Map; Key : in Key_Type);

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procedure Delete (Container : in out Map; Key : in Key_Type);

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procedure Delete (Container : in out Map; Position : in out Cursor);

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procedure Delete_First (Container : in out Map);

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procedure Delete_Last (Container : in out Map);

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function First (Container : Map) return Cursor;

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function First_Element (Container : Map) return Element_Type;

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function First_Key (Container : Map) return Key_Type;

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function Last (Container : Map) return Cursor;

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function Last_Element (Container : Map) return Element_Type;

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function Last_Key (Container : Map) return Key_Type;

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function Next (Position : Cursor) return Cursor;

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procedure Next (Position : in out Cursor);

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function Previous (Position : Cursor) return Cursor;

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procedure Previous (Position : in out Cursor);

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function Find (Container : Map; Key : Key_Type) return Cursor;

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function Element (Container : Map; Key : Key_Type) return Element_Type;

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function Floor (Container : Map; Key : Key_Type) return Cursor;

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function Ceiling (Container : Map; Key : Key_Type) return Cursor;

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function Contains (Container : Map; Key : Key_Type) return Boolean;

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function Has_Element (Position : Cursor) return Boolean;

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function "<" (Left, Right : Cursor) return Boolean;

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function ">" (Left, Right : Cursor) return Boolean;

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function "<" (Left : Cursor; Right : Key_Type) return Boolean;

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function ">" (Left : Cursor; Right : Key_Type) return Boolean;

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function "<" (Left : Key_Type; Right : Cursor) return Boolean;

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function ">" (Left : Key_Type; Right : Cursor) return Boolean;

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procedure Iterate (Container : in Map; Process : not null access procedure (Position : in Cursor));

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procedure Reverse_Iterate (Container : in Map; Process : not null access procedure (Position : in Cursor));

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private

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... -- not specified by the language

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end Ada.Containers.Ordered_Maps;

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Two keys K1 and K2 are equivalent if both K1 < K2 and K2 < K1 return False, using the generic formal "<" operator for keys. Function Equivalent_Keys returns True if Left and Right are equivalent, and False otherwise.

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The actual function for the generic formal function "<" on Key_Type values is expected to return the same value each time it is called with a particular pair of key values. It should define a strict ordering relationship, that is, be irreflexive, asymmetric, and transitive. If the actual for "<" behaves in some other manner, the behavior of this package is unspecified. Which subprograms of this package call "<" and how many times they call it, is unspecified.

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If the value of a key stored in a map is changed other than by an operation in this package such that at least one of "<" or "=" give different results, the behavior of this package is unspecified.

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The first node of a nonempty map is the one whose key is less than the key of all the other nodes in the map. The last node of a nonempty map is the one whose key is greater than the key of all the other elements in the map. The successor of a node is the node with the smallest key that is larger than the key of the given node. The predecessor of a node is the node with the largest key that is smaller than the key of the given node. All comparisons are done using the generic formal "<" operator for keys.

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procedure Delete_First (Container : in out Map);

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If Container is empty, Delete_First has no effect. Otherwise the node designated by First (Container) is removed from Container. Delete_First tampers with the cursors of Container.

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procedure Delete_Last (Container : in out Map);

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If Container is empty, Delete_Last has no effect. Otherwise the node designated by Last (Container) is removed from Container. Delete_Last tampers with the cursors of Container.

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function First_Element (Container : Map) return Element_Type;

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Equivalent to Element (First (Container)).

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function First_Key (Container : Map) return Key_Type;

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Equivalent to Key (First (Container)).

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function Last (Container : Map) return Cursor;

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Returns a cursor that designates the last node in Container. If Container is empty, returns No_Element.

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function Last_Element (Container : Map) return Element_Type;

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Equivalent to Element (Last (Container)).

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function Last_Key (Container : Map) return Key_Type;

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Equivalent to Key (Last (Container)).

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function Previous (Position : Cursor) return Cursor;

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If Position equals No_Element, then Previous returns No_Element. Otherwise Previous returns the a cursor designating the node that precedes the one designated by Position. If Position designates the first element, then Previous returns No_Element.

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procedure Previous (Position : in out Cursor);

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Equivalent to Position := Previous (Position).

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function Floor (Container : Map; Key : Key_Type) return Cursor;

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Floor searches for the last node whose key is not greater than Key, using the generic formal "<" operator for keys. If such a node is found, a cursor that designates it is returned. Otherwise No_Element is returned.

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function Ceiling (Container : Map; Key : Key_Type) return Cursor;

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Ceiling searches for the first node whose key is not less than Key, using the generic formal "<" operator for keys. If such a node is found, a cursor that designates it is returned. Otherwise No_Element is returned.

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function "<" (Left, Right : Cursor) return Boolean;

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Equivalent to Key (Left) < Key (Right).

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function ">" (Left, Right : Cursor) return Boolean;

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Equivalent to Key (Right) < Key (Left).

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function "<" (Left : Cursor; Right : Key_Type) return Boolean;

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Equivalent to Key (Left) < Right.

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function ">" (Left : Cursor; Right : Key_Type) return Boolean;

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Equivalent to Right < Key (Left).

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function "<" (Left : Key_Type; Right : Cursor) return Boolean;

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Equivalent to Left < Key (Right).

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function ">" (Left : Key_Type; Right : Cursor) return Boolean;

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Equivalent to Key (Right) < Left.

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procedure Reverse_Iterate (Container : in Map; Process : not null access procedure (Position : in Cursor));

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Iterates over the nodes in Container as per Iterate, with the difference that the nodes are traversed in predecessor order, starting with the last node.

Implementation Advice

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If N is the length of a map, then the worst-case time complexity of the Element, Insert, Include, Replace, Delete, Exclude and Find operations that take a key parameter should be O((log N)**2) or better. The worst-case time complexity of the subprograms that take a cursor parameter should be O(1).

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