    indexing
    	description: "[
    		Objects representing delayed calls to a function,
    		with some arguments possibly still open.

    		Note: Features are the same as those of ROUTINE,
    			with apply made effective, and the addition
    			of last_result and item.
    	]"
    	legal: "See notice at end of class."
    	status: "See notice at end of class."
    	date: "$Date: 2006-08-21 12:36:06 -0700 (Mon, 21 Aug 2006) $"
    	revision: "$Revision: 62818 $"

    class interface
    	FUNCTION [BASE_TYPE, OPEN_ARGS -> TUPLE create default_create end, RESULT_TYPE]

    create
    	default_create
    			-- Process instances of classes with no creation clause.
    			-- (Default: do nothing.)
    			-- (from ANY)

    feature -- Initialization

    	adapt (other: like Current)
    			-- Initialize from `other'.
    			-- Useful in descendants.
    			-- (from ROUTINE)
    		require -- from ROUTINE
    			other_exists: other /= Void
    			conforming: conforms_to (other)

    feature -- Access

    	apply
    			-- Call function with operands as last set.
    		require -- from ROUTINE
    			valid_operands: valid_operands (operands)

    	call (args: OPEN_ARGS)
    		require -- from ROUTINE
    			valid_operands: valid_operands (args)

    	empty_operands: OPEN_ARGS
    			-- Empty tuple matching open operands
    			-- (from ROUTINE)
    		ensure -- from ROUTINE
    			empty_operands_not_void: Result /= Void

    	generating_type: STRING_8
    			-- Name of current object's generating type
    			-- (type of which it is a direct instance)
    			-- (from ANY)

    	generator: STRING_8
    			-- Name of current object's generating class
    			-- (base class of the type of which it is a direct instance)
    			-- (from ANY)

    	hash_code: INTEGER_32
    			-- Hash code value.
    			-- (from ROUTINE)
    		ensure -- from HASHABLE
    			good_hash_value: Result >= 0

    	item (args: OPEN_ARGS): RESULT_TYPE
    			-- Result of calling function with `args' as operands.
    		require
    			valid_operands: valid_operands (args)

    	last_result: RESULT_TYPE
    			-- Result of last call, if any.

    	frozen operands: OPEN_ARGS
    			-- (from ROUTINE)

    	postcondition (args: like operands): BOOLEAN
    			-- Does current state satisfy routine's
    			-- postcondition for `args'?
    			-- (from ROUTINE)

    	precondition (args: like operands): BOOLEAN
    			-- Do `args' satisfy routine's precondition
    			-- in current state?
    			-- (from ROUTINE)

    	target: ANY
    			-- Target of call.
    			-- (from ROUTINE)

    feature -- Measurement

    	open_count: INTEGER_32
    			-- Number of open operands.
    			-- (from ROUTINE)

    feature -- Comparison

    	frozen deep_equal (some: ANY; other: like arg #1): BOOLEAN
    			-- Are `some' and `other' either both void
    			-- or attached to isomorphic object structures?
    			-- (from ANY)
    		ensure -- from ANY
    			shallow_implies_deep: standard_equal (some, other) implies Result
    			both_or_none_void: (some = Void) implies (Result = (other = Void))
    			same_type: (Result and (some /= Void)) implies some.same_type (other)
    			symmetric: Result implies deep_equal (other, some)

    	frozen equal (some: ANY; other: like arg #1): BOOLEAN
    			-- Are `some' and `other' either both void or attached
    			-- to objects considered equal?
    			-- (from ANY)
    		ensure -- from ANY
    			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 associated function the same as the one
    			-- associated with `other'?
    		require -- from ANY
    			other_not_void: other /= Void
    		ensure -- from ANY
    			symmetric: Result implies other.is_equal (Current)
    			consistent: standard_is_equal (other) implies Result

    	frozen standard_equal (some: ANY; other: like arg #1): BOOLEAN
    			-- Are `some' and `other' either both void or attached to
    			-- field-by-field identical objects of the same type?
    			-- Always uses default object comparison criterion.
    			-- (from ANY)
    		ensure -- from ANY
    			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?
    			-- (from ANY)
    		require -- from ANY
    			other_not_void: other /= Void
    		ensure -- from ANY
    			same_type: Result implies same_type (other)
    			symmetric: Result implies other.standard_is_equal (Current)

    feature -- Status report

    	callable: BOOLEAN is True
    			-- Can routine be called on current object?
    			-- (from ROUTINE)

    	conforms_to (other: ANY): BOOLEAN
    			-- Does type of current object conform to type
    			-- of `other' (as per Eiffel: The Language, chapter 13)?
    			-- (from ANY)
    		require -- from ANY
    			other_not_void: other /= Void

    	is_hashable: BOOLEAN
    			-- May current object be hashed?
    			-- (True if it is not its type's default.)
    			-- (from HASHABLE)
    		ensure -- from HASHABLE
    			ok_if_not_default: Result implies (Current /= default)

    	same_type (other: ANY): BOOLEAN
    			-- Is type of current object identical to type of `other'?
    			-- (from ANY)
    		require -- from ANY
    			other_not_void: other /= Void
    		ensure -- from ANY
    			definition: Result = (conforms_to (other) and other.conforms_to (Current))

    	valid_operands (args: OPEN_ARGS): BOOLEAN
    			-- Are `args' valid operands for this routine?
    			-- (from ROUTINE)

    	valid_target (args: TUPLE): BOOLEAN
    			-- Is the first element of tuple `args' a valid target
    			-- (from ROUTINE)

    feature -- Removal

    	clear_last_result
    			-- Reset content of last_result to its default value

    feature -- Duplication

    	copy (other: like Current)
    			-- Use same function as `other'.
    		require -- from ANY
    			other_not_void: other /= Void
    			type_identity: same_type (other)
    		ensure -- from ANY
    			is_equal: is_equal (other)
    		ensure then -- from ROUTINE
    			same_call_status: other.callable implies callable

    	frozen deep_copy (other: like Current)
    			-- Effect equivalent to that of:
    			--		copy (`other' . deep_twin)
    			-- (from ANY)
    		require -- from ANY
    			other_not_void: other /= Void
    		ensure -- from ANY
    			deep_equal: deep_equal (Current, other)

    	frozen deep_twin: like Current
    			-- New object structure recursively duplicated from Current.
    			-- (from ANY)
    		ensure -- from ANY
    			deep_equal: deep_equal (Current, Result)

    	frozen standard_copy (other: like Current)
    			-- Copy every field of `other' onto corresponding field
    			-- of current object.
    			-- (from ANY)
    		require -- from ANY
    			other_not_void: other /= Void
    			type_identity: same_type (other)
    		ensure -- from ANY
    			is_standard_equal: standard_is_equal (other)

    	frozen standard_twin: like Current
    			-- New object field-by-field identical to `other'.
    			-- Always uses default copying semantics.
    			-- (from ANY)
    		ensure -- from ANY
    			standard_twin_not_void: Result /= Void
    			equal: standard_equal (Result, Current)

    	frozen twin: like Current
    			-- New object equal to `Current'
    			-- twin calls copy; to change copying/twining semantics, redefine copy.
    			-- (from ANY)
    		ensure -- from ANY
    			twin_not_void: Result /= Void
    			is_equal: Result.is_equal (Current)

    feature -- Basic operations

    	frozen default: like Current
    			-- Default value of object's type
    			-- (from ANY)

    	frozen default_pointer: POINTER
    			-- Default value of type `POINTER'
    			-- (Avoid the need to write `p'.default for
    			-- some `p' of type `POINTER'.)
    			-- (from ANY)

    	default_rescue
    			-- Process exception for routines with no Rescue clause.
    			-- (Default: do nothing.)
    			-- (from ANY)

    	frozen do_nothing
    			-- Execute a null action.
    			-- (from ANY)

    feature -- Output

    	io: STD_FILES
    			-- Handle to standard file setup
    			-- (from ANY)

    	out: STRING_8
    			-- New string containing terse printable representation
    			-- of current object
    			-- Was declared in ANY as synonym of tagged_out.
    			-- (from ANY)

    	print (some: ANY)
    			-- Write terse external representation of `some'
    			-- on standard output.
    			-- (from ANY)

    	frozen tagged_out: STRING_8
    			-- New string containing terse printable representation
    			-- of current object
    			-- Was declared in ANY as synonym of out.
    			-- (from ANY)

    feature -- Platform

    	operating_environment: OPERATING_ENVIRONMENT
    			-- Objects available from the operating system
    			-- (from ANY)

    feature -- Settings

    	frozen set_operands (args: OPEN_ARGS)
    			-- Use `args' as operands for next call.
    			-- (from ROUTINE)
    		require -- from ROUTINE
    			valid_operands: valid_operands (args)
    		ensure -- from ROUTINE
    			operands_set: (operands /= Void implies equal (operands, args)) or (operands = Void implies (args = Void or else args.is_empty))

    invariant
    		-- from ROUTINE
    	callable: callable

    		-- from ANY
    	reflexive_equality: standard_is_equal (Current)
    	reflexive_conformance: conforms_to (Current)

    indexing
    	library: "EiffelBase: Library of reusable components for Eiffel."
    	copyright: "Copyright (c) 1984-2006, Eiffel Software and others"
    	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
    	source: "[
    		Eiffel Software
    		356 Storke Road, Goleta, CA 93117 USA
    		Telephone 805-685-1006, Fax 805-685-6869
    		Website http://www.eiffel.com
    		Customer support http://support.eiffel.com
    	]"

    end -- class FUNCTION