1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
5 -- S Y S T E M . V A L _ R E A L --
10 -- Copyright (C) 1992-2000 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 -- Extensive contributions were provided by Ada Core Technologies Inc. --
33 ------------------------------------------------------------------------------
35 with System.Powten_Table; use System.Powten_Table;
36 with System.Val_Util; use System.Val_Util;
38 package body System.Val_Real is
48 return Long_Long_Float
51 pragma Import (C, Reset, "__gnat_init_float");
52 -- We import the floating-point processor reset routine so that we can
53 -- be sure the floating-point processor is properly set for conversion
54 -- calls (see description of Reset in GNAT.Float_Control (g-flocon.ads).
55 -- This is notably need on Windows, where calls to the operating system
56 -- randomly reset the processor into 64-bit mode.
59 -- Local copy of string pointer
61 Base : Long_Long_Float;
64 Uval : Long_Long_Float;
65 -- Accumulated float result
67 subtype Digs is Character range '0' .. '9';
68 -- Used to check for decimal digit
71 -- Power of Base to multiply result by
74 -- Position of starting non-blank character
77 -- Set to True if minus sign is present, otherwise to False
79 Bad_Base : Boolean := False;
80 -- Set True if Base out of range or if out of range digit
82 After_Point : Natural := 0;
83 -- Set to 1 after the point
86 -- Scans integer literal value starting at current character position.
87 -- For each digit encountered, Uval is multiplied by 10.0, and the new
88 -- digit value is incremented. In addition Scale is decremented for each
89 -- digit encountered if we are after the point (After_Point = 1). The
90 -- longest possible syntactically valid numeral is scanned out, and on
91 -- return P points past the last character. On entry, the current
92 -- character is known to be a digit, so a numeral is definitely present.
99 Digit := Character'Pos (Str (P)) - Character'Pos ('0');
100 Uval := Uval * 10.0 + Long_Long_Float (Digit);
102 Scale := Scale - After_Point;
104 -- Done if end of input field
109 -- Check next character
111 elsif Str (P) not in Digs then
112 if Str (P) = '_' then
113 Scan_Underscore (Str, P, Ptr, Max, False);
121 -- Start of processing for System.Scan_Real
125 Scan_Sign (Str, Ptr, Max, Minus, Start);
129 -- If digit, scan numeral before point
131 if Str (P) in Digs then
135 -- Initial point, allowed only if followed by digit (RM 3.5(47))
139 and then Str (P + 1) in Digs
143 -- Any other initial character is an error
146 raise Constraint_Error;
149 -- Deal with based case
151 if P < Max and then (Str (P) = ':' or else Str (P) = '#') then
153 Base_Char : constant Character := Str (P);
155 Fdigit : Long_Long_Float;
158 -- Set bad base if out of range, and use safe base of 16.0,
159 -- to guard against division by zero in the loop below.
161 if Uval < 2.0 or else Uval > 16.0 then
170 -- Special check to allow initial point (RM 3.5(49))
172 if Str (P) = '.' then
177 -- Loop to scan digits of based number. On entry to the loop we
178 -- must have a valid digit. If we don't, then we have an illegal
179 -- floating-point value, and we raise Constraint_Error, note that
180 -- Ptr at this stage was reset to the proper (Start) value.
184 raise Constraint_Error;
186 elsif Str (P) in Digs then
187 Digit := Character'Pos (Str (P)) - Character'Pos ('0');
189 elsif Str (P) in 'A' .. 'F' then
191 Character'Pos (Str (P)) - (Character'Pos ('A') - 10);
193 elsif Str (P) in 'a' .. 'f' then
195 Character'Pos (Str (P)) - (Character'Pos ('a') - 10);
198 raise Constraint_Error;
202 Fdigit := Long_Long_Float (Digit);
204 if Fdigit >= Base then
207 Scale := Scale - After_Point;
208 Uval := Uval * Base + Fdigit;
212 raise Constraint_Error;
214 elsif Str (P) = '_' then
215 Scan_Underscore (Str, P, Ptr, Max, True);
218 -- Skip past period after digit. Note that the processing
219 -- here will permit either a digit after the period, or the
220 -- terminating base character, as allowed in (RM 3.5(48))
222 if Str (P) = '.' and then After_Point = 0 then
227 raise Constraint_Error;
231 exit when Str (P) = Base_Char;
235 -- Based number successfully scanned out (point was found)
240 -- Non-based case, check for being at decimal point now. Note that
241 -- in Ada 95, we do not insist on a decimal point being present
247 if P <= Max and then Str (P) = '.' then
250 -- Scan digits after point if any are present (RM 3.5(46))
252 if P <= Max and then Str (P) in Digs then
260 -- At this point, we have Uval containing the digits of the value as
261 -- an integer, and Scale indicates the negative of the number of digits
262 -- after the point. Base contains the base value (an integral value in
263 -- the range 2.0 .. 16.0). Test for exponent, must be at least one
264 -- character after the E for the exponent to be valid.
266 Scale := Scale + Scan_Exponent (Str, Ptr, Max, Real => True);
268 -- At this point the exponent has been scanned if one is present and
269 -- Scale is adjusted to include the exponent value. Uval contains the
270 -- the integral value which is to be multiplied by Base ** Scale.
272 -- If base is not 10, use exponentiation for scaling
275 Uval := Uval * Base ** Scale;
277 -- For base 10, use power of ten table, repeatedly if necessary.
281 while Scale > Maxpow loop
282 Uval := Uval * Powten (Maxpow);
283 Scale := Scale - Maxpow;
287 Uval := Uval * Powten (Scale);
292 while (-Scale) > Maxpow loop
293 Uval := Uval / Powten (Maxpow);
294 Scale := Scale + Maxpow;
298 Uval := Uval / Powten (-Scale);
302 -- Here is where we check for a bad based number
305 raise Constraint_Error;
307 -- If OK, then deal with initial minus sign, note that this processing
308 -- is done even if Uval is zero, so that -0.0 is correctly interpreted.
324 function Value_Real (Str : String) return Long_Long_Float is
326 P : aliased Integer := Str'First;
329 V := Scan_Real (Str, P'Access, Str'Last);
330 Scan_Trailing_Blanks (Str, P);