1 ------------------------------------------------------------------------------
3 -- GNAT RUNTIME COMPONENTS --
5 -- S Y S T E M . I M G _ D E C --
10 -- Copyright (C) 1992-2001 Free Software Foundation, Inc. --
12 -- GNAT is free software; you can redistribute it and/or modify it under --
13 -- terms of the GNU General Public License as published by the Free Soft- --
14 -- ware Foundation; either version 2, or (at your option) any later ver- --
15 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
16 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
17 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
18 -- for more details. You should have received a copy of the GNU General --
19 -- Public License distributed with GNAT; see file COPYING. If not, write --
20 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
21 -- MA 02111-1307, USA. --
23 -- As a special exception, if other files instantiate generics from this --
24 -- unit, or you link this unit with other files to produce an executable, --
25 -- this unit does not by itself cause the resulting executable to be --
26 -- covered by the GNU General Public License. This exception does not --
27 -- however invalidate any other reasons why the executable file might be --
28 -- covered by the GNU Public License. --
30 -- GNAT was originally developed by the GNAT team at New York University. --
31 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
33 ------------------------------------------------------------------------------
35 with System.Img_Int; use System.Img_Int;
37 package body System.Img_Dec is
43 function Image_Decimal
52 Set_Image_Decimal (V, S, P, Scale, 1, Integer'Max (1, Scale), 0);
54 -- Mess around to make sure we have the objectionable space at the
55 -- start for positive numbers in accordance with the annoying rules!
57 if S (1) /= ' ' and then S (1) /= '-' then
58 S (2 .. P + 1) := S (1 .. P);
60 return S (1 .. P + 1);
66 ------------------------
67 -- Set_Decimal_Digits --
68 ------------------------
70 procedure Set_Decimal_Digits
71 (Digs : in out String;
80 Minus : constant Boolean := (Digs (1) = '-');
81 -- Set True if input is negative
83 Zero : Boolean := (Digs (2) = '0');
84 -- Set True if input is exactly zero (only case when a leading zero
85 -- is permitted in the input string given to this procedure). This
86 -- flag can get set later if rounding causes the value to become zero.
89 -- First digit position of digits remaining to be processed
91 LD : Natural := NDigs;
92 -- Last digit position of digits remaining to be processed
94 ND : Natural := NDigs - 1;
95 -- Number of digits remaining to be processed (LD - FD + 1)
97 Digits_Before_Point : Integer := ND - Scale;
98 -- Number of digits before decimal point in the input value. This
99 -- value can be negative if the input value is less than 0.1, so
100 -- it is an indication of the current exponent. Digits_Before_Point
101 -- is adjusted if the rounding step generates an extra digit.
103 Digits_After_Point : constant Natural := Integer'Max (1, Aft);
104 -- Digit positions after decimal point in result string
107 -- Integer value of exponent
109 procedure Round (N : Natural);
110 -- Round the number in Digs. N is the position of the last digit to be
111 -- retained in the rounded position (rounding is based on Digs (N + 1)
112 -- FD, LD, ND are reset as necessary if required. Note that if the
113 -- result value rounds up (e.g. 9.99 => 10.0), an extra digit can be
114 -- placed in the sign position as a result of the rounding, this is
115 -- the case in which FD is adjusted.
117 procedure Set (C : Character);
119 -- Sets character C in output buffer
121 procedure Set_Blanks_And_Sign (N : Integer);
122 -- Sets leading blanks and minus sign if needed. N is the number of
123 -- positions to be filled (a minus sign is output even if N is zero
124 -- or negative, For a positive value, if N is non-positive, then
125 -- a leading blank is filled.
127 procedure Set_Digits (S, E : Natural);
128 pragma Inline (Set_Digits);
129 -- Set digits S through E from Digs, no effect if S > E
131 procedure Set_Zeroes (N : Integer);
132 pragma Inline (Set_Zeroes);
133 -- Set N zeroes, no effect if N is negative
135 procedure Round (N : Natural) is
139 -- Nothing to do if rounding at or past last digit
144 -- Cases of rounding before the initial digit
148 -- The result is zero, unless we are rounding just before
149 -- the first digit, and the first digit is five or more.
151 if N = 1 and then Digs (2) >= '5' then
158 Digits_Before_Point := Digits_Before_Point + 1;
163 -- Normal case of rounding an existing digit
169 if Digs (N + 1) >= '5' then
170 for J in reverse 2 .. N loop
171 D := Character'Succ (Digs (J));
181 -- Here the rounding overflows into the sign position. That's
182 -- OK, because we already captured the value of the sign and
183 -- we are in any case destroying the value in the Digs buffer
188 Digits_Before_Point := Digits_Before_Point + 1;
193 procedure Set (C : Character) is
199 procedure Set_Blanks_And_Sign (N : Integer) is
217 end Set_Blanks_And_Sign;
219 procedure Set_Digits (S, E : Natural) is
226 procedure Set_Zeroes (N : Integer) is
233 -- Start of processing for Set_Decimal_Digits
236 -- Case of exponent given
239 Set_Blanks_And_Sign (Fore - 1);
246 if ND >= Digits_After_Point then
247 Set_Digits (FD, FD + Digits_After_Point - 1);
251 Set_Zeroes (Digits_After_Point - ND);
254 -- Calculate exponent. The number of digits before the decimal point
255 -- in the input is Digits_Before_Point, and the number of digits
256 -- before the decimal point in the output is 1, so we can get the
257 -- exponent as the difference between these two values. The one
258 -- exception is for the value zero, which by convention has an
264 Expon := Digits_Before_Point - 1;
272 Set_Image_Integer (Expon, Digs, ND);
275 Set_Image_Integer (-Expon, Digs, ND);
278 Set_Zeroes (Exp - ND - 1);
282 -- Case of no exponent given. To make these cases clear, we use
283 -- examples. For all the examples, we assume Fore = 2, Aft = 3.
284 -- A P in the example input string is an implied zero position,
285 -- not included in the input string.
288 -- Round at correct position
289 -- Input: 4PP => unchanged
290 -- Input: 400.03 => unchanged
291 -- Input 3.4567 => 3.457
292 -- Input: 9.9999 => 10.000
293 -- Input: 0.PPP5 => 0.001
294 -- Input: 0.PPP4 => 0
295 -- Input: 0.00003 => 0
297 Round (LD - (Scale - Digits_After_Point));
299 -- No digits before point in input
300 -- Input: .123 Output: 0.123
301 -- Input: .PP3 Output: 0.003
303 if Digits_Before_Point <= 0 then
304 Set_Blanks_And_Sign (Fore - 1);
308 Set_Zeroes (Digits_After_Point - ND);
311 -- At least one digit before point in input
314 Set_Blanks_And_Sign (Fore - Digits_Before_Point);
316 -- Less digits in input than are needed before point
317 -- Input: 1PP Output: 100.000
319 if ND < Digits_Before_Point then
321 Set_Zeroes (Digits_Before_Point - ND);
323 Set_Zeroes (Digits_After_Point);
325 -- Input has full amount of digits before decimal point
328 Set_Digits (FD, FD + Digits_Before_Point - 1);
330 Set_Digits (FD + Digits_Before_Point, LD);
331 Set_Zeroes (Digits_After_Point - (ND - Digits_Before_Point));
336 end Set_Decimal_Digits;
338 -----------------------
339 -- Set_Image_Decimal --
340 -----------------------
342 procedure Set_Image_Decimal
351 Digs : String := Image_Integer (V);
352 -- Sign and digits of decimal value
355 Set_Decimal_Digits (Digs, Digs'Length, S, P, Scale, Fore, Aft, Exp);
356 end Set_Image_Decimal;