1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
5 -- S Y S T E M . V A L _ R E A L --
9 -- Copyright (C) 1992-2003 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, 59 Temple Place - Suite 330, Boston, --
20 -- MA 02111-1307, 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.Powten_Table; use System.Powten_Table;
35 with System.Val_Util; use System.Val_Util;
37 package body System.Val_Real is
47 return Long_Long_Float
50 pragma Import (C, Reset, "__gnat_init_float");
51 -- We import the floating-point processor reset routine so that we can
52 -- be sure the floating-point processor is properly set for conversion
53 -- calls (see description of Reset in GNAT.Float_Control (g-flocon.ads).
54 -- This is notably need on Windows, where calls to the operating system
55 -- randomly reset the processor into 64-bit mode.
58 -- Local copy of string pointer
60 Base : Long_Long_Float;
63 Uval : Long_Long_Float;
64 -- Accumulated float result
66 subtype Digs is Character range '0' .. '9';
67 -- Used to check for decimal digit
70 -- Power of Base to multiply result by
73 -- Position of starting non-blank character
76 -- Set to True if minus sign is present, otherwise to False
78 Bad_Base : Boolean := False;
79 -- Set True if Base out of range or if out of range digit
81 After_Point : Natural := 0;
82 -- Set to 1 after the point
84 Num_Saved_Zeroes : Natural := 0;
85 -- This counts zeroes after the decimal point. A non-zero value means
86 -- that this number of previously scanned digits are zero. if the end
87 -- of the number is reached, these zeroes are simply discarded, which
88 -- ensures that trailing zeroes after the point never affect the value
89 -- (which might otherwise happen as a result of rounding). With this
90 -- processing in place, we can ensure that, for example, we get the
91 -- same exact result from 1.0E+49 and 1.0000000E+49. This is not
92 -- necessarily required in a case like this where the result is not
93 -- a machine number, but it is certainly a desirable behavior.
96 -- Scans integer literal value starting at current character position.
97 -- For each digit encountered, Uval is multiplied by 10.0, and the new
98 -- digit value is incremented. In addition Scale is decremented for each
99 -- digit encountered if we are after the point (After_Point = 1). The
100 -- longest possible syntactically valid numeral is scanned out, and on
101 -- return P points past the last character. On entry, the current
102 -- character is known to be a digit, so a numeral is definitely present.
109 Digit := Character'Pos (Str (P)) - Character'Pos ('0');
112 -- Save up trailing zeroes after the decimal point
114 if Digit = 0 and After_Point = 1 then
115 Num_Saved_Zeroes := Num_Saved_Zeroes + 1;
117 -- Here for a non-zero digit
120 -- First deal with any previously saved zeroes
122 if Num_Saved_Zeroes /= 0 then
123 while Num_Saved_Zeroes > Maxpow loop
124 Uval := Uval * Powten (Maxpow);
125 Num_Saved_Zeroes := Num_Saved_Zeroes - Maxpow;
126 Scale := Scale - Maxpow;
129 Uval := Uval * Powten (Num_Saved_Zeroes);
130 Scale := Scale - Num_Saved_Zeroes;
132 Num_Saved_Zeroes := 0;
135 -- Accumulate new digit
137 Uval := Uval * 10.0 + Long_Long_Float (Digit);
138 Scale := Scale - After_Point;
141 -- Done if end of input field
146 -- Check next character
148 elsif Str (P) not in Digs then
149 if Str (P) = '_' then
150 Scan_Underscore (Str, P, Ptr, Max, False);
158 -- Start of processing for System.Scan_Real
162 Scan_Sign (Str, Ptr, Max, Minus, Start);
166 -- If digit, scan numeral before point
168 if Str (P) in Digs then
172 -- Initial point, allowed only if followed by digit (RM 3.5(47))
176 and then Str (P + 1) in Digs
180 -- Any other initial character is an error
183 raise Constraint_Error;
186 -- Deal with based case
188 if P < Max and then (Str (P) = ':' or else Str (P) = '#') then
190 Base_Char : constant Character := Str (P);
192 Fdigit : Long_Long_Float;
195 -- Set bad base if out of range, and use safe base of 16.0,
196 -- to guard against division by zero in the loop below.
198 if Uval < 2.0 or else Uval > 16.0 then
207 -- Special check to allow initial point (RM 3.5(49))
209 if Str (P) = '.' then
214 -- Loop to scan digits of based number. On entry to the loop we
215 -- must have a valid digit. If we don't, then we have an illegal
216 -- floating-point value, and we raise Constraint_Error, note that
217 -- Ptr at this stage was reset to the proper (Start) value.
221 raise Constraint_Error;
223 elsif Str (P) in Digs then
224 Digit := Character'Pos (Str (P)) - Character'Pos ('0');
226 elsif Str (P) in 'A' .. 'F' then
228 Character'Pos (Str (P)) - (Character'Pos ('A') - 10);
230 elsif Str (P) in 'a' .. 'f' then
232 Character'Pos (Str (P)) - (Character'Pos ('a') - 10);
235 raise Constraint_Error;
238 -- Save up trailing zeroes after the decimal point
240 if Digit = 0 and After_Point = 1 then
241 Num_Saved_Zeroes := Num_Saved_Zeroes + 1;
243 -- Here for a non-zero digit
246 -- First deal with any previously saved zeroes
248 if Num_Saved_Zeroes /= 0 then
249 Uval := Uval * Base ** Num_Saved_Zeroes;
250 Scale := Scale - Num_Saved_Zeroes;
251 Num_Saved_Zeroes := 0;
254 -- Now accumulate the new digit
256 Fdigit := Long_Long_Float (Digit);
258 if Fdigit >= Base then
261 Scale := Scale - After_Point;
262 Uval := Uval * Base + Fdigit;
269 raise Constraint_Error;
271 elsif Str (P) = '_' then
272 Scan_Underscore (Str, P, Ptr, Max, True);
275 -- Skip past period after digit. Note that the processing
276 -- here will permit either a digit after the period, or the
277 -- terminating base character, as allowed in (RM 3.5(48))
279 if Str (P) = '.' and then After_Point = 0 then
284 raise Constraint_Error;
288 exit when Str (P) = Base_Char;
292 -- Based number successfully scanned out (point was found)
297 -- Non-based case, check for being at decimal point now. Note that
298 -- in Ada 95, we do not insist on a decimal point being present
304 if P <= Max and then Str (P) = '.' then
307 -- Scan digits after point if any are present (RM 3.5(46))
309 if P <= Max and then Str (P) in Digs then
317 -- At this point, we have Uval containing the digits of the value as
318 -- an integer, and Scale indicates the negative of the number of digits
319 -- after the point. Base contains the base value (an integral value in
320 -- the range 2.0 .. 16.0). Test for exponent, must be at least one
321 -- character after the E for the exponent to be valid.
323 Scale := Scale + Scan_Exponent (Str, Ptr, Max, Real => True);
325 -- At this point the exponent has been scanned if one is present and
326 -- Scale is adjusted to include the exponent value. Uval contains the
327 -- the integral value which is to be multiplied by Base ** Scale.
329 -- If base is not 10, use exponentiation for scaling
332 Uval := Uval * Base ** Scale;
334 -- For base 10, use power of ten table, repeatedly if necessary.
337 while Scale > Maxpow loop
338 Uval := Uval * Powten (Maxpow);
339 Scale := Scale - Maxpow;
343 Uval := Uval * Powten (Scale);
347 while (-Scale) > Maxpow loop
348 Uval := Uval / Powten (Maxpow);
349 Scale := Scale + Maxpow;
353 Uval := Uval / Powten (-Scale);
357 -- Here is where we check for a bad based number
360 raise Constraint_Error;
362 -- If OK, then deal with initial minus sign, note that this processing
363 -- is done even if Uval is zero, so that -0.0 is correctly interpreted.
379 function Value_Real (Str : String) return Long_Long_Float is
381 P : aliased Integer := Str'First;
384 V := Scan_Real (Str, P'Access, Str'Last);
385 Scan_Trailing_Blanks (Str, P);