note description: "Decimal coefficients. They hold the significant digits. Can be seen as arrays of decimal values. Zero-based index. - Index '0' is the least significant digit, - index 'count-'1 is the most significant digit." library: "Gobo Eiffel Decimal Arithmetic Library" copyright: "Copyright (c) 2004, Paul G. Crismer and others" license: "MIT License" date: "$Date: 2016-05-06 19:15:38 +0000 (Fri, 06 May 2016) $" revision: "$Revision: 98678 $" deferred class MA_DECIMAL_COEFFICIENT inherit KL_COMPARABLE undefine is_equal, copy redefine is_greater end feature {NONE} -- Initialization make (a_capacity: INTEGER_32) -- Make with a_capacity. require a_capacity_positive: a_capacity > 0 deferred ensure capacity_set: capacity >= a_capacity count_zero: count = 0 lower_set: lower = 0 upper_set: upper = capacity - 1 end make_copy (other: like Current) -- Make a copy of other. require other_not_void: other /= Void deferred ensure capacity_set: capacity >= other.capacity equal_other: is_equal (other) end feature -- Access item (index: INTEGER_32): INTEGER_32 -- Item at index require valid_index: valid_index (index) deferred end msd_index: INTEGER_32 -- Index of most significant (non-zero) digit deferred ensure msd_index_small_enough: Result < count msd_index_large_enough: Result >= 0 index_of_msd_or_zero: Result > 0 implies item (Result) /= 0 end feature -- Measurement count: INTEGER_32 -- Number of decimal digits deferred end lower: INTEGER_32 -- Lower index deferred ensure definition: Result = 0 end upper: INTEGER_32 -- Upper index deferred ensure definition: Result <= capacity - 1 end capacity: INTEGER_32 -- Capacity deferred ensure definition: capacity >= count end subcoefficient (index_start, index_end: INTEGER_32): MA_DECIMAL_COEFFICIENT -- Subcoefficient made of digits in range [index_start..index_end] require index_start_big_enough: index_start >= 0 index_end_big_enough: index_end >= index_start index_end_small_enough: index_end <= count - 1 deferred ensure subcoefficient_not_void: Result /= Void end feature -- Status report valid_index (index: INTEGER_32): BOOLEAN -- Is index valid ? do Result := (index >= 0 and then index < count) ensure definition: Result = (index >= 0 and then index < count) end is_zero: BOOLEAN -- Is this coefficient only composed of zeros? local i: INTEGER_32 do Result := True from i := count - 1 until i < 0 loop if item (i) /= 0 then Result := False i := -1 else i := i - 1 end end end is_one: BOOLEAN -- Is Current one? do Result := (msd_index = 0 and then item (0) = 1) ensure definition: Result = (msd_index = 0 and then item (0) = 1) end is_significant: BOOLEAN -- Has Current any non-zero digit? do Result := not is_zero ensure definition: Result = not is_zero end feature {MA_DECIMAL} -- Status setting set_from_substring (s: STRING_8; coefficient_begin, coefficient_end: INTEGER_32) -- Set from s, skip the decimal point if it is present. require s_not_void: s /= Void coefficient_begin: coefficient_begin >= 1 coefficient_end: coefficient_end <= s.count coefficient_end_ge_begin: coefficient_end >= coefficient_begin deferred end feature -- Comparison is_less alias "<" (other: like Current): BOOLEAN -- Is Current less than other? do Result := (three_way_comparison (other) = -1) end is_greater alias ">" (other: like Current): BOOLEAN -- Is Current greater than other? do Result := (three_way_comparison (other) = 1) end feature {MA_DECIMAL, MA_DECIMAL_PARSER, MA_DECIMAL_COEFFICIENT} -- Element change put (v, index: INTEGER_32) -- Put v at index-th item. require valid_index: index >= 0 and index < capacity valid_v: v >= 0 and v <= 9 deferred ensure item_set: item (index) = v adapted_count: (index + 1 > old count) implies count = index + 1 end grow (a_capacity: INTEGER_32) -- Grow coefficient so that it can contain up to a_capacity digits. require a_capacity_large_enough: a_capacity >= count deferred ensure new_capacity: capacity >= a_capacity adapted_count: count = a_capacity end feature -- Duplication to_twin: like Current -- Cloned version of Current deferred ensure twin_not_void: Result /= Void twin_not_current: Result /= Current tiwn_equal_current: Result.is_equal (Current) end feature {MA_DECIMAL, MA_DECIMAL_COEFFICIENT} -- Basic operations integer_add (other: like Current) -- Integer add of other to Current. require other_not_void: other /= Void same_count: count <= other.count deferred ensure new_count: count >= old count end integer_multiply (a, b: like Current) -- Multiply a, b into Current. require a_not_void: a /= Void b_not_void: b /= Void capacity_sufficient: capacity > a.count + b.count deferred end integer_quick_add_msd (other, digits_count: INTEGER_32) -- Integer add of other (between 0 and 9) to Current, -- restricted to digits_count most significant digits. require other_limits: other >= 0 and other <= 9 digits_count: digits_count >= 0 and digits_count <= count deferred ensure new_count: count <= digits_count + 1 end integer_subtract (other: like Current) -- Integer subtract of other to Current, -- provided that result will not be negative. require other_not_void: other /= Void other_smaller: other <= Current deferred end integer_quick_subtract_msd (other, digits_count: INTEGER_32) -- Integer subtract of other (between 0 and 9) to Current -- restricted to digits_count most significant digits. require other_limits: other >= 0 and other <= 9 digits_count: digits_count >= 0 and digits_count <= count deferred ensure new_count: count <= digits_count + 1 end keep_head (a_count: INTEGER_32) -- Keep head of 'a_count' digits. require a_count_valid: a_count > 0 and a_count <= count deferred ensure adapted_count: count = a_count unchanged_capacity: capacity = old capacity end strip_leading_zeroes -- Strip leading zeroes. local index: INTEGER_32 do index := msd_index set_count (index + 1) ensure no_leading_zero: count > 1 implies item (count - 1) /= 0 end shift_left (a_count: INTEGER_32) -- Shift items left. require a_count_greater_zero: a_count > 0 deferred ensure adapted_count: count = old count + a_count zero_shifted: item (0) = 0 end shift_right (a_count: INTEGER_32) -- Shift items right. require a_count_greater_zero: a_count > 0 a_count_less_count: a_count <= count deferred ensure adapted_count: count = old count zero_shifted: item (count - 1) = 0 end feature {MA_DECIMAL} -- Implementation set_count (a_count: INTEGER_32) -- Set count to a_count. require a_count_small_enough: a_count <= capacity a_count_large_enough: a_count >= 0 deferred ensure count_set: count = a_count end invariant count_less_or_equal_capacity: count <= capacity count_not_negative: count >= 0 lower_upper_consistent: lower <= upper end -- class MA_DECIMAL_COEFFICIENT
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