1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- S Y S T E M . I M G _ D E C --
9 -- Copyright (C) 1992-2006, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
29 -- GNAT was originally developed by the GNAT team at New York University. --
30 -- Extensive contributions were provided by Ada Core Technologies Inc. --
32 ------------------------------------------------------------------------------
34 with System.Img_Int; use System.Img_Int;
36 package body System.Img_Dec is
42 function Image_Decimal
44 Scale : Integer) return String
50 Set_Image_Decimal (V, S, P, Scale, 1, Integer'Max (1, Scale), 0);
52 -- Mess around to make sure we have the objectionable space at the
53 -- start for positive numbers in accordance with the annoying rules!
55 if S (1) /= ' ' and then S (1) /= '-' then
56 S (2 .. P + 1) := S (1 .. P);
58 return S (1 .. P + 1);
64 ------------------------
65 -- Set_Decimal_Digits --
66 ------------------------
68 procedure Set_Decimal_Digits
69 (Digs : in out String;
78 Minus : constant Boolean := (Digs (Digs'First) = '-');
79 -- Set True if input is negative
81 Zero : Boolean := (Digs (Digs'First + 1) = '0');
82 -- Set True if input is exactly zero (only case when a leading zero
83 -- is permitted in the input string given to this procedure). This
84 -- flag can get set later if rounding causes the value to become zero.
87 -- First digit position of digits remaining to be processed
89 LD : Natural := NDigs;
90 -- Last digit position of digits remaining to be processed
92 ND : Natural := NDigs - 1;
93 -- Number of digits remaining to be processed (LD - FD + 1)
95 Digits_Before_Point : Integer := ND - Scale;
96 -- Number of digits before decimal point in the input value. This
97 -- value can be negative if the input value is less than 0.1, so
98 -- it is an indication of the current exponent. Digits_Before_Point
99 -- is adjusted if the rounding step generates an extra digit.
101 Digits_After_Point : constant Natural := Integer'Max (1, Aft);
102 -- Digit positions after decimal point in result string
105 -- Integer value of exponent
107 procedure Round (N : Natural);
108 -- Round the number in Digs. N is the position of the last digit to be
109 -- retained in the rounded position (rounding is based on Digs (N + 1)
110 -- FD, LD, ND are reset as necessary if required. Note that if the
111 -- result value rounds up (e.g. 9.99 => 10.0), an extra digit can be
112 -- placed in the sign position as a result of the rounding, this is
113 -- the case in which FD is adjusted.
115 procedure Set (C : Character);
117 -- Sets character C in output buffer
119 procedure Set_Blanks_And_Sign (N : Integer);
120 -- Sets leading blanks and minus sign if needed. N is the number of
121 -- positions to be filled (a minus sign is output even if N is zero
122 -- or negative, For a positive value, if N is non-positive, then
123 -- a leading blank is filled.
125 procedure Set_Digits (S, E : Natural);
126 pragma Inline (Set_Digits);
127 -- Set digits S through E from Digs, no effect if S > E
129 procedure Set_Zeroes (N : Integer);
130 pragma Inline (Set_Zeroes);
131 -- Set N zeroes, no effect if N is negative
133 procedure Round (N : Natural) is
137 -- Nothing to do if rounding at or past last digit
142 -- Cases of rounding before the initial digit
146 -- The result is zero, unless we are rounding just before
147 -- the first digit, and the first digit is five or more.
149 if N = 1 and then Digs (Digs'First + 1) >= '5' then
150 Digs (Digs'First) := '1';
152 Digs (Digs'First) := '0';
156 Digits_Before_Point := Digits_Before_Point + 1;
161 -- Normal case of rounding an existing digit
167 if Digs (N + 1) >= '5' then
168 for J in reverse 2 .. N loop
169 D := Character'Succ (Digs (J));
179 -- Here the rounding overflows into the sign position. That's
180 -- OK, because we already captured the value of the sign and
181 -- we are in any case destroying the value in the Digs buffer
183 Digs (Digs'First) := '1';
186 Digits_Before_Point := Digits_Before_Point + 1;
191 procedure Set (C : Character) is
197 procedure Set_Blanks_And_Sign (N : Integer) is
215 end Set_Blanks_And_Sign;
217 procedure Set_Digits (S, E : Natural) is
224 procedure Set_Zeroes (N : Integer) is
231 -- Start of processing for Set_Decimal_Digits
234 -- Case of exponent given
237 Set_Blanks_And_Sign (Fore - 1);
244 if ND >= Digits_After_Point then
245 Set_Digits (FD, FD + Digits_After_Point - 1);
249 Set_Zeroes (Digits_After_Point - ND);
252 -- Calculate exponent. The number of digits before the decimal point
253 -- in the input is Digits_Before_Point, and the number of digits
254 -- before the decimal point in the output is 1, so we can get the
255 -- exponent as the difference between these two values. The one
256 -- exception is for the value zero, which by convention has an
262 Expon := Digits_Before_Point - 1;
270 Set_Image_Integer (Expon, Digs, ND);
273 Set_Image_Integer (-Expon, Digs, ND);
276 Set_Zeroes (Exp - ND - 1);
280 -- Case of no exponent given. To make these cases clear, we use
281 -- examples. For all the examples, we assume Fore = 2, Aft = 3.
282 -- A P in the example input string is an implied zero position,
283 -- not included in the input string.
286 -- Round at correct position
287 -- Input: 4PP => unchanged
288 -- Input: 400.03 => unchanged
289 -- Input 3.4567 => 3.457
290 -- Input: 9.9999 => 10.000
291 -- Input: 0.PPP5 => 0.001
292 -- Input: 0.PPP4 => 0
293 -- Input: 0.00003 => 0
295 Round (LD - (Scale - Digits_After_Point));
297 -- No digits before point in input
298 -- Input: .123 Output: 0.123
299 -- Input: .PP3 Output: 0.003
301 if Digits_Before_Point <= 0 then
302 Set_Blanks_And_Sign (Fore - 1);
306 Set_Zeroes (Digits_After_Point - ND);
309 -- At least one digit before point in input
312 Set_Blanks_And_Sign (Fore - Digits_Before_Point);
314 -- Less digits in input than are needed before point
315 -- Input: 1PP Output: 100.000
317 if ND < Digits_Before_Point then
319 Set_Zeroes (Digits_Before_Point - ND);
321 Set_Zeroes (Digits_After_Point);
323 -- Input has full amount of digits before decimal point
326 Set_Digits (FD, FD + Digits_Before_Point - 1);
328 Set_Digits (FD + Digits_Before_Point, LD);
329 Set_Zeroes (Digits_After_Point - (ND - Digits_Before_Point));
334 end Set_Decimal_Digits;
336 -----------------------
337 -- Set_Image_Decimal --
338 -----------------------
340 procedure Set_Image_Decimal
349 Digs : String := Image_Integer (V);
350 -- Sign and digits of decimal value
353 Set_Decimal_Digits (Digs, Digs'Length, S, P, Scale, Fore, Aft, Exp);
354 end Set_Image_Decimal;