1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
5 -- S Y S T E M . V A L _ R E A L --
9 -- Copyright (C) 1992-2009, 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 3, 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. --
18 -- As a special exception under Section 7 of GPL version 3, you are granted --
19 -- additional permissions described in the GCC Runtime Library Exception, --
20 -- version 3.1, as published by the Free Software Foundation. --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
27 -- GNAT was originally developed by the GNAT team at New York University. --
28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
30 ------------------------------------------------------------------------------
32 with System.Powten_Table; use System.Powten_Table;
33 with System.Val_Util; use System.Val_Util;
35 package body System.Val_Real is
43 Ptr : not null access Integer;
44 Max : Integer) return Long_Long_Float
47 pragma Import (C, Reset, "__gnat_init_float");
48 -- We import the floating-point processor reset routine so that we can
49 -- be sure the floating-point processor is properly set for conversion
50 -- calls (see description of Reset in GNAT.Float_Control (g-flocon.ads).
51 -- This is notably need on Windows, where calls to the operating system
52 -- randomly reset the processor into 64-bit mode.
55 -- Local copy of string pointer
57 Base : Long_Long_Float;
60 Uval : Long_Long_Float;
61 -- Accumulated float result
63 subtype Digs is Character range '0' .. '9';
64 -- Used to check for decimal digit
67 -- Power of Base to multiply result by
70 -- Position of starting non-blank character
73 -- Set to True if minus sign is present, otherwise to False
75 Bad_Base : Boolean := False;
76 -- Set True if Base out of range or if out of range digit
78 After_Point : Natural := 0;
79 -- Set to 1 after the point
81 Num_Saved_Zeroes : Natural := 0;
82 -- This counts zeroes after the decimal point. A non-zero value means
83 -- that this number of previously scanned digits are zero. If the end
84 -- of the number is reached, these zeroes are simply discarded, which
85 -- ensures that trailing zeroes after the point never affect the value
86 -- (which might otherwise happen as a result of rounding). With this
87 -- processing in place, we can ensure that, for example, we get the
88 -- same exact result from 1.0E+49 and 1.0000000E+49. This is not
89 -- necessarily required in a case like this where the result is not
90 -- a machine number, but it is certainly a desirable behavior.
93 -- Scans integer literal value starting at current character position.
94 -- For each digit encountered, Uval is multiplied by 10.0, and the new
95 -- digit value is incremented. In addition Scale is decremented for each
96 -- digit encountered if we are after the point (After_Point = 1). The
97 -- longest possible syntactically valid numeral is scanned out, and on
98 -- return P points past the last character. On entry, the current
99 -- character is known to be a digit, so a numeral is definitely present.
110 Digit := Character'Pos (Str (P)) - Character'Pos ('0');
113 -- Save up trailing zeroes after the decimal point
115 if Digit = 0 and After_Point = 1 then
116 Num_Saved_Zeroes := Num_Saved_Zeroes + 1;
118 -- Here for a non-zero digit
121 -- First deal with any previously saved zeroes
123 if Num_Saved_Zeroes /= 0 then
124 while Num_Saved_Zeroes > Maxpow loop
125 Uval := Uval * Powten (Maxpow);
126 Num_Saved_Zeroes := Num_Saved_Zeroes - Maxpow;
127 Scale := Scale - Maxpow;
130 Uval := Uval * Powten (Num_Saved_Zeroes);
131 Scale := Scale - Num_Saved_Zeroes;
133 Num_Saved_Zeroes := 0;
136 -- Accumulate new digit
138 Uval := Uval * 10.0 + Long_Long_Float (Digit);
139 Scale := Scale - After_Point;
142 -- Done if end of input field
147 -- Check next character
149 elsif Str (P) not in Digs then
150 if Str (P) = '_' then
151 Scan_Underscore (Str, P, Ptr, Max, False);
159 -- Start of processing for System.Scan_Real
163 Scan_Sign (Str, Ptr, Max, Minus, Start);
167 -- If digit, scan numeral before point
169 if Str (P) in Digs then
173 -- Initial point, allowed only if followed by digit (RM 3.5(47))
177 and then Str (P + 1) in Digs
181 -- Any other initial character is an error
184 raise Constraint_Error;
187 -- Deal with based case
189 if P < Max and then (Str (P) = ':' or else Str (P) = '#') then
191 Base_Char : constant Character := Str (P);
193 Fdigit : Long_Long_Float;
196 -- Set bad base if out of range, and use safe base of 16.0,
197 -- to guard against division by zero in the loop below.
199 if Uval < 2.0 or else Uval > 16.0 then
208 -- Special check to allow initial point (RM 3.5(49))
210 if Str (P) = '.' then
215 -- Loop to scan digits of based number. On entry to the loop we
216 -- must have a valid digit. If we don't, then we have an illegal
217 -- floating-point value, and we raise Constraint_Error, note that
218 -- Ptr at this stage was reset to the proper (Start) value.
222 raise Constraint_Error;
224 elsif Str (P) in Digs then
225 Digit := Character'Pos (Str (P)) - Character'Pos ('0');
227 elsif Str (P) in 'A' .. 'F' then
229 Character'Pos (Str (P)) - (Character'Pos ('A') - 10);
231 elsif Str (P) in 'a' .. 'f' then
233 Character'Pos (Str (P)) - (Character'Pos ('a') - 10);
236 raise Constraint_Error;
239 -- Save up trailing zeroes after the decimal point
241 if Digit = 0 and After_Point = 1 then
242 Num_Saved_Zeroes := Num_Saved_Zeroes + 1;
244 -- Here for a non-zero digit
247 -- First deal with any previously saved zeroes
249 if Num_Saved_Zeroes /= 0 then
250 Uval := Uval * Base ** Num_Saved_Zeroes;
251 Scale := Scale - Num_Saved_Zeroes;
252 Num_Saved_Zeroes := 0;
255 -- Now accumulate the new digit
257 Fdigit := Long_Long_Float (Digit);
259 if Fdigit >= Base then
262 Scale := Scale - After_Point;
263 Uval := Uval * Base + Fdigit;
270 raise Constraint_Error;
272 elsif Str (P) = '_' then
273 Scan_Underscore (Str, P, Ptr, Max, True);
276 -- Skip past period after digit. Note that the processing
277 -- here will permit either a digit after the period, or the
278 -- terminating base character, as allowed in (RM 3.5(48))
280 if Str (P) = '.' and then After_Point = 0 then
285 raise Constraint_Error;
289 exit when Str (P) = Base_Char;
293 -- Based number successfully scanned out (point was found)
298 -- Non-based case, check for being at decimal point now. Note that
299 -- in Ada 95, we do not insist on a decimal point being present
305 if P <= Max and then Str (P) = '.' then
308 -- Scan digits after point if any are present (RM 3.5(46))
310 if P <= Max and then Str (P) in Digs then
318 -- At this point, we have Uval containing the digits of the value as
319 -- an integer, and Scale indicates the negative of the number of digits
320 -- after the point. Base contains the base value (an integral value in
321 -- the range 2.0 .. 16.0). Test for exponent, must be at least one
322 -- character after the E for the exponent to be valid.
324 Scale := Scale + Scan_Exponent (Str, Ptr, Max, Real => True);
326 -- At this point the exponent has been scanned if one is present and
327 -- Scale is adjusted to include the exponent value. Uval contains the
328 -- the integral value which is to be multiplied by Base ** Scale.
330 -- If base is not 10, use exponentiation for scaling
333 Uval := Uval * Base ** Scale;
335 -- For base 10, use power of ten table, repeatedly if necessary
338 while Scale > Maxpow loop
339 Uval := Uval * Powten (Maxpow);
340 Scale := Scale - Maxpow;
344 Uval := Uval * Powten (Scale);
348 while (-Scale) > Maxpow loop
349 Uval := Uval / Powten (Maxpow);
350 Scale := Scale + Maxpow;
354 Uval := Uval / Powten (-Scale);
358 -- Here is where we check for a bad based number
361 raise Constraint_Error;
363 -- If OK, then deal with initial minus sign, note that this processing
364 -- 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;
383 V := Scan_Real (Str, P'Access, Str'Last);
384 Scan_Trailing_Blanks (Str, P);