Annotated King Reference Manual/Types

This page is work in progress. Type Declarations Some general principles: All scalar subtypes have a default value. For bounded numeric and enumeration subtypes, this is the 'First of the subtype, unless a different value is specified with the Default_Value aspect. For unbounded numeric subtypes, the Default_Value aspect must be specified. Note that an unbounded numeric type can have bounded subtypes. The Predicate aspect may be specified for all subtypes. All scalar types have the attributes 'Image, 'Value, 'Min, 'Max, 'Previous, and 'Next. Integer and enumeration types have the attributes 'Position, 'Value (integer), 'Representation, and 'From_Representation. For integer types, 'Position and 'Representation both give the value of the parameter, and 'Value (integer) and 'From_Representation give the value of the type with the value of the parameter (if that exists); this is similar to 'Pos and "Val for integer types in Ada. 'Image <=>, 'Value (string) are inverses of each other, as are 'Position <=> 'Value (integer) Syntax type_declaration ::= full_type_declaration | hidden_type_declaration full_type_declaration ::= type defining_identifier [known_discriminant_part] is type_definition [aspect_specification]; hidden_type_declaration ::=   type defining_identifier [discriminant_part] is hidden [aspect_specification]; discriminant_part ::= unknown_discriminant_part | known_discriminant_part unknown_discriminant_part ::= (<>) known_discriminant_part ::= (discriminant_specification {; discriminant_specification}) discriminant_specification ::= defining_identifier : subtype_mark [<- default_expression]   type_definition ::=             enumeration_type_definition           | integer_type_definition           | real_type_definition           | map_type_definition           | sequence_type_definition           | set_type_definition           | record_type_definition           | derived_type_definition           | module_type_definition           | task_type_definition Rationale - Discussion - Enumeration Types Examples type Suit is (Spade, Club, Heart, Diamond); type Philosopher_ID is (Archimedes, Descartes, Hegel, Kant, Socrates); Syntax enumeration_type_definition ::= (enumeration_literal_specification {, enumeration_literal_specification}) enumeration_literal_specification ::= defining_identifier | defining_character_literal Operators = /= < <= > >= Attributes First, Last, Position, From_Representation, Representation, Image, Value, Min, Max, Previous, Next Aspects Bit_Size, Byte_Size Object declaration My_Card : Suit; Rationale - Discussion - Integer Types Examples Bounded integer types type Day is range 1 .. 31; Unbounded integer types type Factorial is range <> with Default_Value => 0; Syntax integer_type_definition ::= bounded_integer_type_definition | unbounded_integer_type_definition bounded_integer_type_definition ::= range static_simple_expression .. static_simple_expression unbounded_integer_type_definition ::= range <> Operators + - * / rem mod ^ = /= < <= > >= and or xor not Attributes First, Last, Bit_Wise_Operators, Image, Value, Min, Max, Previous, Next, Valid Additional attributes with Bit_Wise_Operators = True: Shift_Left, Shift_Right, Rotate_Left, Rotate_Right, Mod Aspects Default_Value, Predicate, Signed_Representation, Overflow_Checking Object declaration N : Factorial; Rationale Bit-wise operations are available for the base type of all bounded integer types that fit in a single hardware integer. Discussion - Real Types Syntax real_type_definition ::= floating_point_definition | fixed_point_definition Floating Point Types Examples Bounded floating-Point Types type Risk is digits 7 range 0 .. 1; Unbounded floating-Point Types type Rational is digits <> with Default_Value => 0; Syntax floating_point_definition ::= bounded_floating_point_definition | unbounded_floating_point_definition bounded_floating_point_definition ::= digits static_expression [real_range_specification] real_range_specification ::= range static_simple_expression .. static_simple_expression unbounded_floating_point_definition ::= digits <> Operators + - * / ^ = /= < <= > >= Attributes Image, Value, Min, Max, Previous, Next, Valid, digits Aspects Default_Value, Predicate Object declaration Speed : Rational; Rationale - Discussion - Fixed Point Types Examples Bounded fixed-Point Types type Angle is delta 0.01 range -3.14 .. 3.14; Unbounded fixed-Point Types type Duration is delta 10.0 ^ -9 range <> with Default_Value => 0; Syntax fixed_point_definition ::= bounded_fixed_point_definition | unbounded_fixed_point_definition bounded_fixed_point_definition ::= delta static_expression real_range_specification unbounded_fixed_point_definition ::= delta static_expression range <> Operators + - * / ^ = /= < <= > >= Attributes Image, Value, Min, Max, Previous, Next, Valid, delta Aspects Default_Value, Predicate Object declaration Bearing : Angle; Rationale Shouldn't decimal types be available, in order to cover the corresponding available type of Ada? A King fixed-point type with a delta that is a power of 10 is equivalent to an Ada decimal fixed-point type. type Money is delta 0.01 digits 14; The above would be equivalent to: type Money is delta 0.01 range -999_999_999_999.99 .. 999_999_999_999.99; Discussion - Map Types Examples type Store is map Part_Key => Stock_Info; Syntax map_type_definition := map key_subtype_mark => value_subtype_mark Operators = /= "=" is only defined if it is defined for the value subtype. Attributes - Operations Delete, Clear, Defined, Size Aspects - Object declaration My_Store : Store; Component deference My_Store (K99) Aggregates Store'(K1 => SI1, KE => SIE) Store'(null) -- Empty map Iteration for K in My_Store'range for E of My_Store Rationale Maps may also be implemented by functions, so King uses a common notation for both. Discussion - Sequence Types Examples type Stack is sequence of Message; Syntax sequence_type_definition := sequence of element_subtype_mark Operators = /= & "=" is only defined if it is defined for the value subtype. Attributes - Operations Delete, Clear, Length Aspects - Object declaration My_Stack : Stack; Component deference My_Stack [Curent] Aggregates My_Stack'[MC, ML, MZ] My_Stack'[null] -- Empty sequence Iteration for P in [reverse] My_Stack'range for E of [reverse] My_Stack Rationale - Discussion - Set Types Examples type File_Mask is set of File_Mode; Syntax set_type_definition := set of element_subtype_mark Operators + - * / = /= < <= > >= [not] in Attributes - Operations Size Aspects - Object declaration My_Mask : File_Mask: Component deference - Aggregates My_Mask'{Read, Exec} My_Mask'{null} -- Empty set My_Mask'{all} -- Full set Iteration for M of My_Mask Rationale - Discussion - Record Types Examples type Complex is record Re : Float; Im : Float; end record Complex; Syntax record_type_definition ::= record_definition record_definition ::=            record               component_list            end record record_identifier component_list ::= component_item {component_item}           | {component_item} variant_part           | null; component_item ::= component_declaration component_declaration ::= defining_identifier : component_definition [<- default_expression]                 [aspect_specification]; component_definition ::= subtype_indication variant_part ::= case discriminant_direct_name is               variant               {variant}           end case; variant ::= when discrete_choice_list =>               component_list discrete_choice_list ::= discrete_choice {| discrete_choice} discrete_choice ::= choice_expression | discrete_subtype_indication | range_specification | others Operators = /= Attributes - Aspects - Object declaration Z : Complex; Component deference Z.Re Rationale - Discussion - Derived Types Examples type Boxes (Length : Position_Value) is record Box_A : Receive_Box (Max_Length => Length); Box_B : Receive_Box (Max_Length => Length); end record; type Boxes_4 is new Boxes (Length => 4); Syntax derived_type_definition ::= new parent_subtype_indication Operators - Attributes - Aspects - Rationale The operations, attributes, and so on are based on the parent type. Discussion - Module Types Examples type Strings is module Set : procedure (S : String); Index : function (Pattern : String; Going : Direction <- Forward) return Position_Value; Head : function (Count : Natural; Pad : Unicode <- Space) return String; -- ... end module Strings; Syntax module_type_definition ::= module           subprogram_declaration {subprogram_declaration}         end module module_identifier Operators - Attributes - Aspects - Rationale - Discussion - Active Task Types Examples type Philosopher (ID : Philosopher_ID <- Archimedes) is task; Syntax task_type_definition ::= task Operators = /= Attributes - Aspects - Object declaration T1 : Philosopher; Rationale - Discussion - Passive Task Types Examples type Semaphore is task Secure : procedure; Release : procedure; end task Semaphore; Syntax task_type_definition ::= task               subprogram_declaration {subprogram_declaration}             end task task_identifier Operators = /= Attributes - Aspects - Object declaration S1 : Semaphore; Rationale Passive tasks are the only way that active tasks may communicate. Discussion -