note
	description: "DECIMAL numbers. Following the 'General Decimal Arithmetic Specification'."
	library: "Gobo Eiffel Decimal Arithmetic Library"
	copyright: "Copyright (c) 2004-2018, 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

create 
	make_from_integer,
	make_from_string,
	make_from_string_ctx,
	make_copy,
	make_zero,
	make_one,
	make


create {MA_DECIMAL}
	make_infinity,
	make_nan,
	make_snan,
	make_special


create {MA_DECIMAL_TEXT_PARSER}
	make_from_parser

feature -- Access

	sign: INTEGER_32
			-- Sign: positive = 1; negative = -1
		ensure
			definition1: Result = -1 implies is_negative
			definition2: Result = 1 implies is_positive

	exponent: INTEGER_32
			-- Current exponent

	hash_code: INTEGER_32
			-- Hash code value
	
feature -- Constants

	one: like Current
			-- Neutral element for "*" and "/"
		ensure then
			instance_free: class
			one_is_one: Result.is_one
			one_is_positive: not Result.is_negative

	Minus_one: MA_DECIMAL
			-- Minus one
		ensure
			instance_free: class
			minus_one_not_void: Result /= Void
			is_minus_one: Result.is_one and then Result.is_negative

	zero: like Current
			-- Neutral element for "+" and "-"
		ensure then
			instance_free: class
			is_zero: Result.is_zero

	Negative_zero: MA_DECIMAL
			-- Negative zero
		ensure
			instance_free: class
			negative_zero_not_void: Result /= Void
			is_zero: Result.is_zero
			is_negative: Result.is_negative

	Nan: MA_DECIMAL
			-- Not a Number
		ensure
			instance_free: class
			nan_not_void: Result /= Void
			is_nan: Result.is_nan

	Snan: MA_DECIMAL
			-- Signaling Not a Number
		ensure
			instance_free: class
			snan_not_void: Result /= Void
			is_snan: Result.is_signaling_nan

	Infinity: MA_DECIMAL
			-- Infinity
		ensure
			instance_free: class
			infinity_not_void: Result /= Void
			is_infinity: Result.is_infinity
			is_positive: Result.is_positive

	Negative_infinity: MA_DECIMAL
			-- Negative infinity
		ensure
			instance_free: class
			negative_infinity_not_void: Result /= Void
			is_infinity: Result.is_infinity
			is_negative: Result.is_negative
	
feature -- Status report

	is_integer: BOOLEAN
			-- Is this an integer?
			-- (i.e no fractional part other than all zeroes)

	is_double: BOOLEAN
			-- Is this a double?

	divisible (other: like Current): BOOLEAN
			-- May current object be divided by other?
		ensure then
			definition: Result = not other.is_zero

	exponentiable (other: NUMERIC): BOOLEAN
			-- May current object be elevated to the power other?

	is_negative: BOOLEAN
			-- Is the number negative?

	is_positive: BOOLEAN
			-- Is the number positive?
		ensure
			definition: Result = not is_negative

	is_nan: BOOLEAN
			-- Is this "Not a Number" (NaN)?
		ensure
			definition: Result = (is_signaling_nan or is_quiet_nan)

	is_special: BOOLEAN
			-- Is this a special value?
		ensure
			definition: Result = (is_nan or else is_infinity)

	is_signaling_nan: BOOLEAN
			-- Is this a "Signaling NaN"?

	is_quiet_nan: BOOLEAN
			-- Is this a "Quiet NaN"?

	is_infinity: BOOLEAN
			-- Is this an Infinity?

	is_zero: BOOLEAN
			-- Is this a Zero value?
		ensure
			definition: Result = (not is_special and then coefficient.is_zero)

	is_one: BOOLEAN
			-- Is this a One ?
		ensure
			definition: Result = (not is_special and then exponent = 0 and then coefficient.is_one)
	
feature -- Basic operations

	product alias "*" (other: like Current): like Current
			-- Product by other
		ensure then
			product_not_void: Result /= Void

	identity alias "+": like Current
			-- Unary plus
		ensure then
			unary_plus_not_void: Result /= Void

	binary_plus alias "+" (other: like Current): like Current
			-- Sum with other (commutative)
		ensure then
			sum_not_void: Result /= Void

	opposite alias "-": like Current
			-- Unary minus
		ensure then
			unary_minus_not_void: Result /= Void

	binary_minus alias "-" (other: like Current): like Current
			-- Result of subtracting other
		ensure then
			subtract_not_void: Result /= Void

	quotient alias "/" (other: like Current): like Current
			-- Division by other
		ensure then
			division_not_void: Result /= Void

	integer_remainder alias "\\" (other: like Current): like Current
			-- Remainder of integer division
		ensure
			remainder_not_void: Result /= Void

	integer_quotient alias "//" (other: like Current): like Current
			-- Integer division
		ensure
			integer_division_not_void: Result /= Void

	power alias "^" (other: NUMERIC): MA_DECIMAL
			-- Current decimal to the power other

	is_less alias "<" (other: like Current): BOOLEAN
			-- Is current decimal less than other?
	
feature -- Measurement

	count: INTEGER_32
			-- Count of significant digits
		ensure
			zero_when_special: is_special implies Result = 0
	
feature -- Comparison

	is_equal (other: like Current): BOOLEAN
			-- Are Current and other considered equal?
	
feature -- Conversion

	out: STRING_8
			-- Printable representation

	to_double: REAL_64
			-- Current as a DOUBLE
		require
			is_double: is_double

	to_integer: INTEGER_32
			-- Current as an INTEGER
		require
			is_integer: is_integer
			large_enough: Current >= Decimal.Minimum_integer
			small_enough: Current <= Decimal.Maximum_integer

	to_integer_ctx (ctx: MA_DECIMAL_CONTEXT): INTEGER_32
			-- Current as an INTEGER wrt ctx
		require
			is_integer: is_integer
			large_enough: Current >= Decimal.Minimum_integer
			small_enough: Current <= Decimal.Maximum_integer

	to_engineering_string: STRING_8
			-- Current as a string in engineering notation format
		ensure
			to_string_not_void: Result /= Void

	to_scientific_string: STRING_8
			-- Current as a string in scientific notation format
		ensure
			to_string_not_void: Result /= Void
	
feature -- Duplication

	copy (other: like Current)
			-- Copy other to current decimal.
	
feature -- Basic operations

	add (other: like Current; ctx: MA_DECIMAL_CONTEXT): like Current
			-- Add other with respect to the ctx context
		require
			other_not_void: other /= Void
			ctx_not_void: ctx /= Void
		ensure
			add_not_void: Result /= Void

	subtract (other: like Current; ctx: MA_DECIMAL_CONTEXT): like Current
			-- Subtract other with respect to the ctx context
		require
			other_not_void: other /= Void
			ctx_not_void: ctx /= Void
		ensure
			subtract_not_void: Result /= Void

	multiply (other: like Current; ctx: MA_DECIMAL_CONTEXT): like Current
			-- Multiply other with respect to ctx
		require
			other_not_void: other /= Void
			ctx_not_void: ctx /= Void
		ensure
			multiply_not_void: Result /= Void

	divide (other: like Current; ctx: MA_DECIMAL_CONTEXT): like Current
			-- Divide Current by other whith respect to ctx
		require
			other_not_void: other /= Void
			ctx_not_void: ctx /= Void
		ensure
			divide_not_void: Result /= Void

	divide_integer (other: like Current; ctx: MA_DECIMAL_CONTEXT): like Current
			-- Integer division of Current by other whith respect to ctx
		require
			other_not_void: other /= Void
			ctx_not_void: ctx /= Void
		ensure
			divide_integer_not_void: Result /= Void

	remainder (other: like Current; ctx: MA_DECIMAL_CONTEXT): like Current
			-- Remainder of integer division of Current by other whith respect to ctx
		require
			other_not_void: other /= Void
			ctx_not_void: ctx /= Void
		ensure
			remainder_not_void: Result /= Void

	rescale (new_exponent: INTEGER_32; ctx: MA_DECIMAL_CONTEXT): like Current
			-- Decimal from Current rescaled to new_exponent
		require
			ctx_not_void: ctx /= Void
		ensure
			rescale_not_void: Result /= Void

	rescale_decimal (new_exponent: like Current; ctx: MA_DECIMAL_CONTEXT): like Current
			-- Rescale using decimal new_exponent
		require
			new_exponent_not_void: new_exponent /= Void
			ctx_not_void: ctx /= Void
		ensure
			rescale_decimal_not_void: Result /= Void

	round_to_integer (ctx: MA_DECIMAL_CONTEXT): like Current
			-- Round to an integer with exponent 0
		require
			ctx_not_void: ctx /= Void
		ensure
			round_to_integer_not_void: Result /= Void
			definition: not Result.is_special implies Result.exponent = 0

	plus (ctx: MA_DECIMAL_CONTEXT): like Current
			-- Prefix "+" with respect to the ctx context
		require
			ctx_not_void: ctx /= Void
		ensure
			plus_not_void: Result /= Void

	normalize: like Current
			-- Normalized version of current decimal
		ensure
			normalize_not_void: Result /= Void

	minus (ctx: MA_DECIMAL_CONTEXT): like Current
			-- Prefix "-" with respect to the ctx context
		require
			ctx_not_void: ctx /= Void
		ensure
			minus_not_void: Result /= Void

	abs: like Current
			-- Absolute value of Current
		ensure
			abs_not_void: Result /= Void

	abs_ctx (ctx: MA_DECIMAL_CONTEXT): like Current
			-- Absolute value of Current relative to ctx
		require
			ctx_not_void: ctx /= Void
		ensure
			abs_ctx_not_void: Result /= Void
			definition: Result.sign >= 0

	max_ctx (other: like Current; ctx: MA_DECIMAL_CONTEXT): like Current
			-- Max between Current and other relative to ctx
		require
			other_not_void: other /= Void
			ctx_not_void: ctx /= Void
		ensure
			max_ctx_not_void: Result /= Void

	min_ctx (other: like Current; ctx: MA_DECIMAL_CONTEXT): like Current
			-- Min between Current and other relative to ctx
		require
			other_not_void: other /= Void
			ctx_not_void: ctx /= Void
		ensure
			min_ctx_not_void: Result /= Void

	compare (other: like Current; ctx: MA_DECIMAL_CONTEXT): like Current
			-- Compare value of Current and other;
			-- Result = 0 if Current = other,
			-- Result = -1 if Current < other,
			-- Result = +1 if Current > other.
		require
			other_not_void: other /= Void
			ctx_not_void: ctx /= Void
		ensure
			compare_not_void: Result /= Void
	
invariant
	special_values: special >= Special_none and then special <= Special_quiet_nan
	coefficient_not_void: coefficient /= Void
	special_share_coefficient: is_special implies coefficient = Special_coefficient
	special_has_exponent_zero: is_special implies exponent = 0
	special_coefficient_is_zero: Special_coefficient.is_zero

end -- class MA_DECIMAL

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