note
	description: "User selectable parameters and rules which govern the results of decimal arithmetic operations"
	library: "Gobo Eiffel Decimal Arithmetic Library"
	copyright: "Copyright (c) 2004, Paul G. Crismer and others"
	license: "MIT License"
	date: "$Date: 2019-02-07 22:54:15 +0000 (Thu, 07 Feb 2019) $"
	revision: "$Revision: 102807 $"

class interface
	MA_DECIMAL_CONTEXT

create 
	make_default
			-- Create a new default context for general purpose arithmetic (IEEE 854), single precision.
		ensure
			default_digits: digits = Default_digits
			default_rounding_mode: rounding_mode = Default_rounding_mode
			trap_division_by_zero: is_trapped (Signal_division_by_zero)
			trap_invalid_operation: is_trapped (Signal_invalid_operation)
			trap_overflow: is_trapped (Signal_overflow)
			trap_underflow: is_trapped (Signal_underflow)

	make_double
			-- Create a new double precision context.
		ensure
			default_digits: digits = 2 * Default_digits + 1
			default_rounding_mode: rounding_mode = Default_rounding_mode
			trap_division_by_zero: is_trapped (Signal_division_by_zero)
			trap_invalid_operation: is_trapped (Signal_invalid_operation)
			trap_overflow: is_trapped (Signal_overflow)
			trap_underflow: is_trapped (Signal_underflow)

	make_extended
			-- Create a new extended default context (IEEE 854), single precision.
		ensure
			default_digits: digits = Default_digits
			default_rounding_mode: rounding_mode = Round_half_even

	make_double_extended
			-- Create a new extented default context, double precision.
		ensure
			default_digits: digits = 2 * Default_digits + 1
			default_rounding_mode: rounding_mode = Round_half_even

	make (a_digits, a_rounding_mode: INTEGER_32)
			-- Create a new math context.
		require
			a_digits_valid: a_digits >= Minimum_digits and a_digits <= Maximum_digits
			a_rounding_mode_valid: Integer_array_.has (Rounds, a_rounding_mode)
		ensure
			digits_set: digits = a_digits
			rounding_mode_set: rounding_mode = a_rounding_mode
			exponent_limit: exponent_limit = Maximum_exponent

feature -- Access

	Any_array_: KL_ARRAY_ROUTINES [detachable ANY]
			-- Routines that ought to be in class ARRAY
			-- (from KL_IMPORTED_ARRAY_ROUTINES)
		ensure -- from KL_IMPORTED_ARRAY_ROUTINES
			instance_free: class
			any_array_routines_not_void: Result /= Void

	Array_special_integer_: KL_ARRAY_ROUTINES [detachable SPECIAL [INTEGER_32]]
			-- Routines that ought to be in class ARRAY
			-- (from KL_IMPORTED_ARRAY_ROUTINES)
		ensure -- from KL_IMPORTED_ARRAY_ROUTINES
			instance_free: class
			special_integer_array_routines_not_void: Result /= Void

	Boolean_array_: KL_ARRAY_ROUTINES [BOOLEAN]
			-- Routines that ought to be in class ARRAY
			-- (from KL_IMPORTED_ARRAY_ROUTINES)
		ensure -- from KL_IMPORTED_ARRAY_ROUTINES
			instance_free: class
			boolean_array_routines_not_void: Result /= Void

	Detachable_string_array_routines: KL_ARRAY_ROUTINES [detachable STRING_8]
			-- Routines that ought to be in class ARRAY
			-- (from KL_IMPORTED_ARRAY_ROUTINES)
		ensure -- from KL_IMPORTED_ARRAY_ROUTINES
			instance_free: class
			detachable_string_array_routines_not_void: Result /= Void

	digits: INTEGER_32
			-- Number of digits (precision) to be used for an operation.
			-- The DECIMAL operators use this value to determine the precision of results.
			-- Note that leading zeros (in the integer part of a number) are never significant.

	e_tiny: INTEGER_32
			-- Minimum value of the exponent for subnormal numbers

	Exceptions: KL_EXCEPTIONS
			-- Exception handling
			-- (from KL_SHARED_EXCEPTIONS)
		ensure -- from KL_SHARED_EXCEPTIONS
			instance_free: class
			exceptions_not_void: Result /= Void

	exponent_limit: INTEGER_32
			-- Exponent limit;
			-- Exponents can range from -exponent_limit through +exponent_limit

	generating_type: TYPE [detachable MA_DECIMAL_CONTEXT]
			-- Type of current object
			-- (type of which it is a direct instance)
			-- (from ANY)
		ensure -- from ANY
			generating_type_not_void: Result /= Void

	generator: STRING_8
			-- Name of current object's generating class
			-- (base class of the type of which it is a direct instance)
			-- (from ANY)
		ensure -- from ANY
			generator_not_void: Result /= Void
			generator_not_empty: not Result.is_empty

	Integer_array_: KL_ARRAY_ROUTINES [INTEGER_32]
			-- Routines that ought to be in class ARRAY
			-- (from KL_IMPORTED_ARRAY_ROUTINES)
		ensure -- from KL_IMPORTED_ARRAY_ROUTINES
			instance_free: class
			integer_array_routines_not_void: Result /= Void

	precision: INTEGER_32
			-- Synonym for 'digits'
		ensure
			synonym_of_digits: Result = digits

	reason: detachable STRING_8
			-- Reason of latest raised signal

	rounding_mode: INTEGER_32
			-- Rounding algorithm to be used for an operation when non-zero digits have to
			-- be discarded in order to reduce the precision of a result

	String_: KL_STRING_ROUTINES
			-- Routines that ought to be in class STRING
			-- (from KL_IMPORTED_STRING_ROUTINES)
		ensure -- from KL_IMPORTED_STRING_ROUTINES
			instance_free: class
			string_routines_not_void: Result /= Void

	String_array_: KL_ARRAY_ROUTINES [detachable STRING_8]
			-- Routines that ought to be in class ARRAY
			-- (from KL_IMPORTED_ARRAY_ROUTINES)
		ensure -- from KL_IMPORTED_ARRAY_ROUTINES
			instance_free: class
			string_array_routines_not_void: Result /= Void

	String_array_routines: KL_ARRAY_ROUTINES [STRING_8]
			-- Routines that ought to be in class ARRAY
			-- (from KL_IMPORTED_ARRAY_ROUTINES)
		ensure -- from KL_IMPORTED_ARRAY_ROUTINES
			instance_free: class
			string_array_routines_not_void: Result /= Void
	
feature -- Comparison

	frozen deep_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void
			-- or attached to isomorphic object structures?
			-- (from ANY)
		ensure -- from ANY
			instance_free: class
			shallow_implies_deep: standard_equal (a, b) implies Result
			both_or_none_void: (a = Void) implies (Result = (b = Void))
			same_type: (Result and (a /= Void)) implies (b /= Void and then a.same_type (b))
			symmetric: Result implies deep_equal (b, a)

	frozen equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached
			-- to objects considered equal?
			-- (from ANY)
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.is_equal (b))

	frozen is_deep_equal (other: MA_DECIMAL_CONTEXT): BOOLEAN
			-- Are Current and other attached to isomorphic object structures?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			shallow_implies_deep: standard_is_equal (other) implies Result
			same_type: Result implies same_type (other)
			symmetric: Result implies other.is_deep_equal (Current)

	is_equal (other: like Current): BOOLEAN
			-- Is other equal to Current?
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			symmetric: Result implies other ~ Current
			consistent: standard_is_equal (other) implies Result

	frozen standard_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b 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
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.standard_is_equal (b))

	frozen standard_is_equal (other: MA_DECIMAL_CONTEXT): 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

	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

	exception_on_trap: BOOLEAN
			-- Should an exception be raised when trap occurs?

	is_extended: BOOLEAN
			-- Is current context extended?

	is_flagged (a_signal: INTEGER_32): BOOLEAN
			-- Is a_signal flagged?
		require
			valid_signal: valid_signal (a_signal)

	is_trapped (a_signal: INTEGER_32): BOOLEAN
			-- Is a_signal trapped?
		require
			valid_signal: valid_signal (a_signal)

	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_signal (a_signal: INTEGER_32): BOOLEAN
			-- Is a_signal a valid one?
	
feature -- Element change

	disable_exception_on_trap
			-- Disable exception when trap occurs.

	disable_trap (a_signal: INTEGER_32)
			-- Enable trapping of a_signal.
		require
			valid_signal: valid_signal (a_signal)
		ensure
			not_trapped_signal: not is_trapped (a_signal)

	enable_exception_on_trap
			-- Enable exception when trap occurs.

	enable_trap (a_signal: INTEGER_32)
			-- Enable trapping of a_signal.
		require
			valid_signal: valid_signal (a_signal)
		ensure
			trapped_signal: is_trapped (a_signal)

	reset_flag (a_signal: INTEGER_32)
			-- Reset a_signal.
		require
			valid_signal: valid_signal (a_signal)
		ensure
			unflagged_signal: not is_flagged (a_signal)

	reset_flags
			-- Reset all signals to zero.

	set_digits (some_digits: INTEGER_32)
			-- Set digits to some_digits.
		require
			some_digits_valid: some_digits >= Minimum_digits and some_digits <= Maximum_digits
		ensure
			digits_set: digits = some_digits

	set_exponent_limit (a_limit: INTEGER_32)
			-- Set exponent_limit to a_limit.
		require
			limit_positive: a_limit >= 0
		ensure
			limit_set: exponent_limit = a_limit

	set_extended
			-- Set is_extended to True.
		ensure
			extended: is_extended

	set_flag (a_signal: INTEGER_32)
			-- Flag a_signal.
		require
			valid_signal: valid_signal (a_signal)
		ensure
			flagged_signal: is_flagged (a_signal)

	set_normal
			-- Set is_extended to False.
		ensure
			normal: not is_extended

	set_rounding_mode (a_mode: INTEGER_32)
			-- Set rounding_mode to a_mode.
		require
			valid_mode: Integer_array_.has (Rounds, a_mode)
		ensure
			rounding_mode_set: rounding_mode = a_mode
	
feature -- Conversion

	out: STRING_8
			-- Printable representation
		ensure -- from ANY
			out_not_void: Result /= Void
	
feature -- Duplication

	cloned_object: MA_DECIMAL_CONTEXT
			-- Clone of current object
			-- (from KL_CLONABLE)
		ensure -- from KL_CLONABLE
			cloned_not_void: Result /= Void
			same_type: Any_.same_types (Result, Current)
			is_equal: Result.is_equal (Current)

	copy (other: like Current)
			-- Copy other.
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		ensure -- from ANY
			is_equal: Current ~ other

	frozen deep_copy (other: MA_DECIMAL_CONTEXT)
			-- 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: MA_DECIMAL_CONTEXT
			-- New object structure recursively duplicated from Current.
			-- (from ANY)
		ensure -- from ANY
			deep_twin_not_void: Result /= Void
			deep_equal: deep_equal (Current, Result)

	frozen standard_copy (other: MA_DECIMAL_CONTEXT)
			-- 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: MA_DECIMAL_CONTEXT
			-- 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: MA_DECIMAL_CONTEXT
			-- New object equal to Current
			-- twin calls copy; to change copying/twinning semantics, redefine copy.
			-- (from ANY)
		ensure -- from ANY
			twin_not_void: Result /= Void
			is_equal: Result ~ Current
	
feature -- Basic operations

	frozen default: detachable MA_DECIMAL_CONTEXT
			-- 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)
		ensure -- from ANY
			instance_free: class

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

	frozen do_nothing
			-- Execute a null action.
			-- (from ANY)
		ensure -- from ANY
			instance_free: class

	signal (a_signal: INTEGER_32; a_message: STRING_8)
			-- Raise flag a_signal for a_message reason.
		require
			valid_signal: valid_signal (a_signal)
			a_message_not_void: a_message /= Void
		ensure
			flagged_signal: is_flagged (a_signal)
			reason_set: reason = a_message
	
feature -- Constants: defaults

	Default_digits: INTEGER_32 = 9
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Default_rounding_mode: INTEGER_32
			-- Default rounding mode
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)
		ensure -- from MA_DECIMAL_CONTEXT_CONSTANTS
			instance_free: class
			definition: Result = Round_half_up

	Default_traps: ARRAY [INTEGER_32]
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)
		ensure -- from MA_DECIMAL_CONTEXT_CONSTANTS
			instance_free: class
			default_traps_not_void: Result /= Void
			has_division_by_zero: Integer_array_.has (Result, Signal_division_by_zero)
			has_invalid_operation: Integer_array_.has (Result, Signal_invalid_operation)
			has_overflow: Integer_array_.has (Result, Signal_overflow)
			has_underflow: Integer_array_.has (Result, Signal_underflow)
	
feature -- Constants: limits

	Maximum_digits: INTEGER_32 = 999999999
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Maximum_exponent: INTEGER_32 = 999999999
			-- Maximum exponent allowed
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Minimum_digits: INTEGER_32 = 1
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Minimum_exponent: INTEGER_32 = -999999999
			-- Minimum exponent allowed
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)
	
feature -- Constants: rounding modes

	Round_ceiling: INTEGER_32 = 2
			-- Rounding mode to round to a more positive number;
			-- All discarded digits are ignored (truncated). The result is neither incremented nor decremented.
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Round_down: INTEGER_32 = 1
			-- Rounding mode to round towards zero;
			-- If any of the discarded digits are non-zero then the result should be rounded towards the next ore negative digit.
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Round_floor: INTEGER_32 = 3
			-- Rounding mode to round to a more negative number;
			-- If any of the discarded digits are non-zero then the result should be rounded towards the next more negative digit.
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Round_half_down: INTEGER_32 = 5
			-- Rounding mode to round to nearest neighbor, where an equidistant value is rounded down;
			-- If the discarded digits represent greater than half (0.5 times)
			-- the value of a one in the next position then the result should be
			-- rounded up (away from zero). Otherwise the discarded digits are ignored.
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Round_half_even: INTEGER_32 = 6
			-- Rounding mode to round to nearest neighbor, where an equidistant value is rounded to the nearest even neighbor;
			-- If the discarded digits represent greater than half (0.5 times) the value of a one in the next position then the result should be
			-- rounded up (away from zero).
			-- If they represent less than half, then the result should be rounded down.
			-- Otherwise (they represent exactly half) the result is rounded down if its rightmost digit is even, or rounded up if its
			-- rightmost digit is odd (to make an even digit).
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Round_half_up: INTEGER_32 = 4
			-- Rounding mode to round to nearest neighbor, where an equidistant value is rounded up;
			-- If the discarded digits represent greater than or equal to half (0.5 times) the value
			-- of a one in the next position then the result should be rounded up (away from zero).
			-- Otherwise the discarded digits are ignored.
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Round_unnecessary: INTEGER_32 = 7
			-- Rounding mode to assert that no rounding is necessary;
			-- Rounding (potential loss of information) is not permitted.
			-- If any of the discarded digits are non-zero then an 'ArithmeticException'should be thrown.
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Round_up: INTEGER_32 = 0
			-- Rounding mode to round away from zero;
			-- If any of the discarded digits are non-zero then the result will be rounded up (away from zero).
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)
	
feature -- Constants: signals

	Signal_division_by_zero: INTEGER_32 = 1
			-- Non Zero dividend is divided by zero
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Signal_inexact: INTEGER_32 = 2
			-- A result is not exact, or overflows or underflows without being trapped
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Signal_invalid_operation: INTEGER_32 = 3
			-- A result would be undefined or impossible
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Signal_lost_digits: INTEGER_32 = 4
			-- Non-zero digits have been discarded before an operation
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Signal_overflow: INTEGER_32 = 5
			-- The exponent of a result is too large to be represented
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Signal_rounded: INTEGER_32 = 6
			-- A result has been rounded, that is, some zero or non-zero digits were discarded
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Signal_subnormal: INTEGER_32 = 8
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Signal_underflow: INTEGER_32 = 7
			-- The exponent of a result is too small to be represented
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)
	
feature -- Constants: special flags

	Special_infinity: INTEGER_32 = 1
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Special_none: INTEGER_32 = 0
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Special_quiet_nan: INTEGER_32 = 3
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)

	Special_signaling_nan: INTEGER_32 = 2
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)
	
feature -- Constants: support

	Round_words: ARRAY [STRING_8]
			-- Textual representation of rounding modes
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)
		ensure -- from MA_DECIMAL_CONTEXT_CONSTANTS
			instance_free: class
			round_word_not_void: Result /= Void
			no_void_round_words: not Any_array_.has (Result, Void)

	Rounds: ARRAY [INTEGER_32]
			-- Rounding modes
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)
		ensure -- from MA_DECIMAL_CONTEXT_CONSTANTS
			instance_free: class
			rounds_not_void: Result /= Void

	Signal_words: ARRAY [STRING_8]
			-- Textual representation of signals
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)
		ensure -- from MA_DECIMAL_CONTEXT_CONSTANTS
			instance_free: class
			signal_words_not_void: Result /= Void
			no_void_signal_words: not Any_array_.has (Result, Void)

	Signals: ARRAY [INTEGER_32]
			-- Signals
			-- (from MA_DECIMAL_CONTEXT_CONSTANTS)
		ensure -- from MA_DECIMAL_CONTEXT_CONSTANTS
			instance_free: class
			signals_not_void: Result /= Void
	
feature -- Output

	Io: STD_FILES
			-- Handle to standard file setup
			-- (from ANY)
		ensure -- from ANY
			instance_free: class
			io_not_void: Result /= Void

	print (o: detachable ANY)
			-- Write terse external representation of o
			-- on standard output.
			-- (from ANY)
		ensure -- from ANY
			instance_free: class

	frozen tagged_out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		ensure -- from ANY
			tagged_out_not_void: Result /= Void
	
feature -- Platform

	Operating_environment: OPERATING_ENVIRONMENT
			-- Objects available from the operating system
			-- (from ANY)
		ensure -- from ANY
			instance_free: class
			operating_environment_not_void: Result /= Void
	
invariant
	positive_digits: digits >= 0
	rounding_mode_valid: rounding_mode = Round_ceiling or rounding_mode = Round_down or rounding_mode = Round_floor or rounding_mode = Round_half_down or rounding_mode = Round_half_even or rounding_mode = Round_half_up or rounding_mode = Round_unnecessary or rounding_mode = Round_up
	flags_not_void: flags /= Void
	flags_lower: flags.lower = Signal_division_by_zero
	flags_upper: flags.upper = Signal_subnormal
	traps_not_void: traps /= Void
	traps_lower: traps.lower = Signal_division_by_zero
	traps_upper: traps.upper = Signal_subnormal

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

end -- class MA_DECIMAL_CONTEXT

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