1 ------------------------------------------------------------------------------
3 -- GNAT RUNTIME COMPONENTS --
5 -- S Y S T E M . I M G _ D E C --
11 -- Copyright (C) 1992-2001 Free Software Foundation, Inc. --
13 -- GNAT is free software; you can redistribute it and/or modify it under --
14 -- terms of the GNU General Public License as published by the Free Soft- --
15 -- ware Foundation; either version 2, or (at your option) any later ver- --
16 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
17 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
18 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
19 -- for more details. You should have received a copy of the GNU General --
20 -- Public License distributed with GNAT; see file COPYING. If not, write --
21 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
22 -- MA 02111-1307, USA. --
24 -- As a special exception, if other files instantiate generics from this --
25 -- unit, or you link this unit with other files to produce an executable, --
26 -- this unit does not by itself cause the resulting executable to be --
27 -- covered by the GNU General Public License. This exception does not --
28 -- however invalidate any other reasons why the executable file might be --
29 -- covered by the GNU Public License. --
31 -- GNAT was originally developed by the GNAT team at New York University. --
32 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
34 ------------------------------------------------------------------------------
36 with System.Img_Int; use System.Img_Int;
38 package body System.Img_Dec is
44 function Image_Decimal
53 Set_Image_Decimal (V, S, P, Scale, 1, Integer'Max (1, Scale), 0);
55 -- Mess around to make sure we have the objectionable space at the
56 -- start for positive numbers in accordance with the annoying rules!
58 if S (1) /= ' ' and then S (1) /= '-' then
59 S (2 .. P + 1) := S (1 .. P);
61 return S (1 .. P + 1);
67 ------------------------
68 -- Set_Decimal_Digits --
69 ------------------------
71 procedure Set_Decimal_Digits
72 (Digs : in out String;
81 Minus : constant Boolean := (Digs (1) = '-');
82 -- Set True if input is negative
84 Zero : Boolean := (Digs (2) = '0');
85 -- Set True if input is exactly zero (only case when a leading zero
86 -- is permitted in the input string given to this procedure). This
87 -- flag can get set later if rounding causes the value to become zero.
90 -- First digit position of digits remaining to be processed
92 LD : Natural := NDigs;
93 -- Last digit position of digits remaining to be processed
95 ND : Natural := NDigs - 1;
96 -- Number of digits remaining to be processed (LD - FD + 1)
98 Digits_Before_Point : Integer := ND - Scale;
99 -- Number of digits before decimal point in the input value. This
100 -- value can be negative if the input value is less than 0.1, so
101 -- it is an indication of the current exponent. Digits_Before_Point
102 -- is adjusted if the rounding step generates an extra digit.
104 Digits_After_Point : constant Natural := Integer'Max (1, Aft);
105 -- Digit positions after decimal point in result string
108 -- Integer value of exponent
110 procedure Round (N : Natural);
111 -- Round the number in Digs. N is the position of the last digit to be
112 -- retained in the rounded position (rounding is based on Digs (N + 1)
113 -- FD, LD, ND are reset as necessary if required. Note that if the
114 -- result value rounds up (e.g. 9.99 => 10.0), an extra digit can be
115 -- placed in the sign position as a result of the rounding, this is
116 -- the case in which FD is adjusted.
118 procedure Set (C : Character);
120 -- Sets character C in output buffer
122 procedure Set_Blanks_And_Sign (N : Integer);
123 -- Sets leading blanks and minus sign if needed. N is the number of
124 -- positions to be filled (a minus sign is output even if N is zero
125 -- or negative, For a positive value, if N is non-positive, then
126 -- a leading blank is filled.
128 procedure Set_Digits (S, E : Natural);
129 pragma Inline (Set_Digits);
130 -- Set digits S through E from Digs, no effect if S > E
132 procedure Set_Zeroes (N : Integer);
133 pragma Inline (Set_Zeroes);
134 -- Set N zeroes, no effect if N is negative
136 procedure Round (N : Natural) is
140 -- Nothing to do if rounding at or past last digit
145 -- Cases of rounding before the initial digit
149 -- The result is zero, unless we are rounding just before
150 -- the first digit, and the first digit is five or more.
152 if N = 1 and then Digs (2) >= '5' then
159 Digits_Before_Point := Digits_Before_Point + 1;
164 -- Normal case of rounding an existing digit
170 if Digs (N + 1) >= '5' then
171 for J in reverse 2 .. N loop
172 D := Character'Succ (Digs (J));
182 -- Here the rounding overflows into the sign position. That's
183 -- OK, because we already captured the value of the sign and
184 -- we are in any case destroying the value in the Digs buffer
189 Digits_Before_Point := Digits_Before_Point + 1;
194 procedure Set (C : Character) is
200 procedure Set_Blanks_And_Sign (N : Integer) is
218 end Set_Blanks_And_Sign;
220 procedure Set_Digits (S, E : Natural) is
227 procedure Set_Zeroes (N : Integer) is
234 -- Start of processing for Set_Decimal_Digits
237 -- Case of exponent given
240 Set_Blanks_And_Sign (Fore - 1);
247 if ND >= Digits_After_Point then
248 Set_Digits (FD, FD + Digits_After_Point - 1);
252 Set_Zeroes (Digits_After_Point - ND);
255 -- Calculate exponent. The number of digits before the decimal point
256 -- in the input is Digits_Before_Point, and the number of digits
257 -- before the decimal point in the output is 1, so we can get the
258 -- exponent as the difference between these two values. The one
259 -- exception is for the value zero, which by convention has an
265 Expon := Digits_Before_Point - 1;
273 Set_Image_Integer (Expon, Digs, ND);
276 Set_Image_Integer (-Expon, Digs, ND);
279 Set_Zeroes (Exp - ND - 1);
283 -- Case of no exponent given. To make these cases clear, we use
284 -- examples. For all the examples, we assume Fore = 2, Aft = 3.
285 -- A P in the example input string is an implied zero position,
286 -- not included in the input string.
289 -- Round at correct position
290 -- Input: 4PP => unchanged
291 -- Input: 400.03 => unchanged
292 -- Input 3.4567 => 3.457
293 -- Input: 9.9999 => 10.000
294 -- Input: 0.PPP5 => 0.001
295 -- Input: 0.PPP4 => 0
296 -- Input: 0.00003 => 0
298 Round (LD - (Scale - Digits_After_Point));
300 -- No digits before point in input
301 -- Input: .123 Output: 0.123
302 -- Input: .PP3 Output: 0.003
304 if Digits_Before_Point <= 0 then
305 Set_Blanks_And_Sign (Fore - 1);
309 Set_Zeroes (Digits_After_Point - ND);
312 -- At least one digit before point in input
315 Set_Blanks_And_Sign (Fore - Digits_Before_Point);
317 -- Less digits in input than are needed before point
318 -- Input: 1PP Output: 100.000
320 if ND < Digits_Before_Point then
322 Set_Zeroes (Digits_Before_Point - ND);
324 Set_Zeroes (Digits_After_Point);
326 -- Input has full amount of digits before decimal point
329 Set_Digits (FD, FD + Digits_Before_Point - 1);
331 Set_Digits (FD + Digits_Before_Point, LD);
332 Set_Zeroes (Digits_After_Point - (ND - Digits_Before_Point));
337 end Set_Decimal_Digits;
339 -----------------------
340 -- Set_Image_Decimal --
341 -----------------------
343 procedure Set_Image_Decimal
352 Digs : String := Image_Integer (V);
353 -- Sign and digits of decimal value
356 Set_Decimal_Digits (Digs, Digs'Length, S, P, Scale, Fore, Aft, Exp);
357 end Set_Image_Decimal;