1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
5 -- S Y S T E M . V A L _ R E A L --
11 -- Copyright (C) 1992-2000 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.Powten_Table; use System.Powten_Table;
37 with System.Val_Util; use System.Val_Util;
39 package body System.Val_Real is
49 return Long_Long_Float
52 pragma Import (C, Reset, "__gnat_init_float");
53 -- We import the floating-point processor reset routine so that we can
54 -- be sure the floating-point processor is properly set for conversion
55 -- calls (see description of Reset in GNAT.Float_Control (g-flocon.ads).
56 -- This is notably need on Windows, where calls to the operating system
57 -- randomly reset the processor into 64-bit mode.
60 -- Local copy of string pointer
62 Base : Long_Long_Float;
65 Uval : Long_Long_Float;
66 -- Accumulated float result
68 subtype Digs is Character range '0' .. '9';
69 -- Used to check for decimal digit
72 -- Power of Base to multiply result by
75 -- Position of starting non-blank character
78 -- Set to True if minus sign is present, otherwise to False
80 Bad_Base : Boolean := False;
81 -- Set True if Base out of range or if out of range digit
83 After_Point : Natural := 0;
84 -- Set to 1 after the point
87 -- Scans integer literal value starting at current character position.
88 -- For each digit encountered, Uval is multiplied by 10.0, and the new
89 -- digit value is incremented. In addition Scale is decremented for each
90 -- digit encountered if we are after the point (After_Point = 1). The
91 -- longest possible syntactically valid numeral is scanned out, and on
92 -- return P points past the last character. On entry, the current
93 -- character is known to be a digit, so a numeral is definitely present.
100 Digit := Character'Pos (Str (P)) - Character'Pos ('0');
101 Uval := Uval * 10.0 + Long_Long_Float (Digit);
103 Scale := Scale - After_Point;
105 -- Done if end of input field
110 -- Check next character
112 elsif Str (P) not in Digs then
113 if Str (P) = '_' then
114 Scan_Underscore (Str, P, Ptr, Max, False);
122 -- Start of processing for System.Scan_Real
126 Scan_Sign (Str, Ptr, Max, Minus, Start);
130 -- If digit, scan numeral before point
132 if Str (P) in Digs then
136 -- Initial point, allowed only if followed by digit (RM 3.5(47))
140 and then Str (P + 1) in Digs
144 -- Any other initial character is an error
147 raise Constraint_Error;
150 -- Deal with based case
152 if P < Max and then (Str (P) = ':' or else Str (P) = '#') then
154 Base_Char : constant Character := Str (P);
156 Fdigit : Long_Long_Float;
159 -- Set bad base if out of range, and use safe base of 16.0,
160 -- to guard against division by zero in the loop below.
162 if Uval < 2.0 or else Uval > 16.0 then
171 -- Special check to allow initial point (RM 3.5(49))
173 if Str (P) = '.' then
178 -- Loop to scan digits of based number. On entry to the loop we
179 -- must have a valid digit. If we don't, then we have an illegal
180 -- floating-point value, and we raise Constraint_Error, note that
181 -- Ptr at this stage was reset to the proper (Start) value.
185 raise Constraint_Error;
187 elsif Str (P) in Digs then
188 Digit := Character'Pos (Str (P)) - Character'Pos ('0');
190 elsif Str (P) in 'A' .. 'F' then
192 Character'Pos (Str (P)) - (Character'Pos ('A') - 10);
194 elsif Str (P) in 'a' .. 'f' then
196 Character'Pos (Str (P)) - (Character'Pos ('a') - 10);
199 raise Constraint_Error;
203 Fdigit := Long_Long_Float (Digit);
205 if Fdigit >= Base then
208 Scale := Scale - After_Point;
209 Uval := Uval * Base + Fdigit;
213 raise Constraint_Error;
215 elsif Str (P) = '_' then
216 Scan_Underscore (Str, P, Ptr, Max, True);
219 -- Skip past period after digit. Note that the processing
220 -- here will permit either a digit after the period, or the
221 -- terminating base character, as allowed in (RM 3.5(48))
223 if Str (P) = '.' and then After_Point = 0 then
228 raise Constraint_Error;
232 exit when Str (P) = Base_Char;
236 -- Based number successfully scanned out (point was found)
241 -- Non-based case, check for being at decimal point now. Note that
242 -- in Ada 95, we do not insist on a decimal point being present
248 if P <= Max and then Str (P) = '.' then
251 -- Scan digits after point if any are present (RM 3.5(46))
253 if P <= Max and then Str (P) in Digs then
261 -- At this point, we have Uval containing the digits of the value as
262 -- an integer, and Scale indicates the negative of the number of digits
263 -- after the point. Base contains the base value (an integral value in
264 -- the range 2.0 .. 16.0). Test for exponent, must be at least one
265 -- character after the E for the exponent to be valid.
267 Scale := Scale + Scan_Exponent (Str, Ptr, Max, Real => True);
269 -- At this point the exponent has been scanned if one is present and
270 -- Scale is adjusted to include the exponent value. Uval contains the
271 -- the integral value which is to be multiplied by Base ** Scale.
273 -- If base is not 10, use exponentiation for scaling
276 Uval := Uval * Base ** Scale;
278 -- For base 10, use power of ten table, repeatedly if necessary.
282 while Scale > Maxpow loop
283 Uval := Uval * Powten (Maxpow);
284 Scale := Scale - Maxpow;
288 Uval := Uval * Powten (Scale);
293 while (-Scale) > Maxpow loop
294 Uval := Uval / Powten (Maxpow);
295 Scale := Scale + Maxpow;
299 Uval := Uval / Powten (-Scale);
303 -- Here is where we check for a bad based number
306 raise Constraint_Error;
308 -- If OK, then deal with initial minus sign, note that this processing
309 -- is done even if Uval is zero, so that -0.0 is correctly interpreted.
325 function Value_Real (Str : String) return Long_Long_Float is
327 P : aliased Integer := Str'First;
330 V := Scan_Real (Str, P'Access, Str'Last);
331 Scan_Trailing_Blanks (Str, P);