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5 SHORT FORMS OF REQUIRED CLASSES

5.1 Class GENERAL

indexing

description: "Platform--independent universal properties. This class is an ancestor to all developer-written classes."

class interface

feature -- Access

generating_type: STRING

-- Name of current object's generating type

-- (type of which it is a direct instance)

generator: STRING

-- Name of current object's generating class

-- (base class of the type of which it is a direct instance)

id_object (id: INTEGER): ANY

-- Object for which object_id has returned id;

-- void if none.

object_id: INTEGER

-- Value identifying current object uniquely;

-- meaningful only for reference types.

stripped (other: GENERAL): like other

-- New object with fields copied from current object,

-- but limited to attributes of type of other.

require

conformance: conforms_to (other)

ensure

stripped_to_other: Result.same_type (other)

feature -- Status report

frozen conforms_to (other: GENERAL): BOOLEAN

-- Does type of current object conform to type

-- of other (as per Eiffel: The Language, chapter13)?

require

other_not_void: other /= Void

frozen same_type (other: GENERAL): BOOLEAN

-- Is type of current object identical to type of other?

require

other_not_void: other /= Void

ensure

definition: Result = (conforms_to (other) and other.conforms_to (Current))

feature -- Comparison

frozen deep_equal (some: GENERAL; other: like some): BOOLEAN

-- Are some and other either both void

-- or attached to isomorphic object structures?

ensure

shallow_implies_deep: standard_equal (some, other) implies Result;

same_type: Result implies some.same_type (other);

symmetric: Result implies deep_equal (other, some)

frozen equal (some: GENERAL; other: like some): BOOLEAN

-- Are some and other either both void or attached

-- to objects considered equal?

ensure

definition: Result = (some = Void and other = Void) or else ((some /= Void and other /= Void) and then some.is_equal (other));

is_equal (other: like Current): BOOLEAN

-- Is other attached to an object considered equal

-- to current object?

require

other_not_void: other /= Void

ensure

consistent: standard_is_equal (other) implies Result;

same_type: Result implies same_type (other);

symmetric: Result implies other.is_equal (Current)

frozen standard_equal (some: GENERAL; other: like some): BOOLEAN

-- Are some and other either both void or attached to

-- field--by-field identical objects of the same type?

-- Always uses the default object comparison criterion.

ensure

definition: Result = (some = Void and other = Void) or else ((some /= Void and other /= Void) and then some.standard_is_equal (other))

frozen standard_is_equal (other: like Current): BOOLEAN

-- Is other attached to an object of the same type as

-- current object, and field--by-field identical to it?

require

other_not_void: other /= Void

ensure

same_type: Result implies same_type (other);

symmetric: Result implies other.standard_is_equal (Current)

feature -- Duplication

frozen clone (other: GENERAL): like other

-- Void if other is void; otherwise new object

-- equal to other.

ensure

equal: equal (Result, other)

copy (other: like Current)

-- Update current object using fields of object attached

-- to other, so as to yield equal objects.

require

other_not_void: other /= Void;

type_identity: same_type (other)

ensure

is_equal: is_equal (other)

frozen deep_clone (other: GENERAL): like other

-- Void if other is void: otherwise, new object structure

-- recursively duplicated from the one attached to other

deep_equal: deep_equal (other, Result)

frozen standard_clone (other: GENERAL): like other

-- Void if other is void; otherwise new object

-- field--by-field identical to other.

-- Always uses the default copying semantics.

ensure

equal: standard_equal (Result, other)

frozen standard_copy (other: like Current)

-- Copy every field of other onto corresponding field

-- of current object.

require

other_not_void: other /= Void;

type_identity: same_type (other)

ensure

is_standard_equal: standard_is_equal (other)

feature -- Basic operations

frozen default: like Current

-- Default value of current type

frozen default_pointer: POINTER

-- Default value of type POINTER

-- (Avoid the need to write p.default for some p

-- of type POINTER.)

ensure

Result = Result.default

default_rescue

-- Handle exception if no Rescue clause.

-- (Default: do nothing.)

frozen do_nothing

-- Execute a null action.

frozen Void: NONE

-- Void reference

feature -- Output

io: STD_FILES

-- Handle to standard file setup

out: STRING

-- New string containing terse printable representation

-- of current object

print (some: GENERAL)

-- Write terse external representation of some on

-- standard output.

frozen tagged_out: STRING

-- New string containing printable representation of

-- current object, each field preceded by its attribute

-- name, a colon and a space.

invariant

reflexive_equality: standard_is_equal (Current);

reflexive_conformance: conforms_to (Current);

involutive_object_id: id_object (object_id) = Current

end

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