1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
5 -- S Y S T E M . V A L _ R E A L --
9 -- Copyright (C) 1992-2005, 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
.Powten_Table
; use System
.Powten_Table
;
35 with System
.Val_Util
; use System
.Val_Util
;
37 package body System
.Val_Real
is
46 Max
: Integer) return Long_Long_Float
49 pragma Import
(C
, Reset
, "__gnat_init_float");
50 -- We import the floating-point processor reset routine so that we can
51 -- be sure the floating-point processor is properly set for conversion
52 -- calls (see description of Reset in GNAT.Float_Control (g-flocon.ads).
53 -- This is notably need on Windows, where calls to the operating system
54 -- randomly reset the processor into 64-bit mode.
57 -- Local copy of string pointer
59 Base
: Long_Long_Float;
62 Uval
: Long_Long_Float;
63 -- Accumulated float result
65 subtype Digs
is Character range '0' .. '9';
66 -- Used to check for decimal digit
69 -- Power of Base to multiply result by
72 -- Position of starting non-blank character
75 -- Set to True if minus sign is present, otherwise to False
77 Bad_Base
: Boolean := False;
78 -- Set True if Base out of range or if out of range digit
80 After_Point
: Natural := 0;
81 -- Set to 1 after the point
83 Num_Saved_Zeroes
: Natural := 0;
84 -- This counts zeroes after the decimal point. A non-zero value means
85 -- that this number of previously scanned digits are zero. if the end
86 -- of the number is reached, these zeroes are simply discarded, which
87 -- ensures that trailing zeroes after the point never affect the value
88 -- (which might otherwise happen as a result of rounding). With this
89 -- processing in place, we can ensure that, for example, we get the
90 -- same exact result from 1.0E+49 and 1.0000000E+49. This is not
91 -- necessarily required in a case like this where the result is not
92 -- a machine number, but it is certainly a desirable behavior.
95 -- Scans integer literal value starting at current character position.
96 -- For each digit encountered, Uval is multiplied by 10.0, and the new
97 -- digit value is incremented. In addition Scale is decremented for each
98 -- digit encountered if we are after the point (After_Point = 1). The
99 -- longest possible syntactically valid numeral is scanned out, and on
100 -- return P points past the last character. On entry, the current
101 -- character is known to be a digit, so a numeral is definitely present.
112 Digit
:= Character'Pos (Str
(P
)) - Character'Pos ('0');
115 -- Save up trailing zeroes after the decimal point
117 if Digit
= 0 and After_Point
= 1 then
118 Num_Saved_Zeroes
:= Num_Saved_Zeroes
+ 1;
120 -- Here for a non-zero digit
123 -- First deal with any previously saved zeroes
125 if Num_Saved_Zeroes
/= 0 then
126 while Num_Saved_Zeroes
> Maxpow
loop
127 Uval
:= Uval
* Powten
(Maxpow
);
128 Num_Saved_Zeroes
:= Num_Saved_Zeroes
- Maxpow
;
129 Scale
:= Scale
- Maxpow
;
132 Uval
:= Uval
* Powten
(Num_Saved_Zeroes
);
133 Scale
:= Scale
- Num_Saved_Zeroes
;
135 Num_Saved_Zeroes
:= 0;
138 -- Accumulate new digit
140 Uval
:= Uval
* 10.0 + Long_Long_Float (Digit
);
141 Scale
:= Scale
- After_Point
;
144 -- Done if end of input field
149 -- Check next character
151 elsif Str
(P
) not in Digs
then
152 if Str
(P
) = '_' then
153 Scan_Underscore
(Str
, P
, Ptr
, Max
, False);
161 -- Start of processing for System.Scan_Real
165 Scan_Sign
(Str
, Ptr
, Max
, Minus
, Start
);
169 -- If digit, scan numeral before point
171 if Str
(P
) in Digs
then
175 -- Initial point, allowed only if followed by digit (RM 3.5(47))
179 and then Str
(P
+ 1) in Digs
183 -- Any other initial character is an error
186 raise Constraint_Error
;
189 -- Deal with based case
191 if P
< Max
and then (Str
(P
) = ':' or else Str
(P
) = '#') then
193 Base_Char
: constant Character := Str
(P
);
195 Fdigit
: Long_Long_Float;
198 -- Set bad base if out of range, and use safe base of 16.0,
199 -- to guard against division by zero in the loop below.
201 if Uval
< 2.0 or else Uval
> 16.0 then
210 -- Special check to allow initial point (RM 3.5(49))
212 if Str
(P
) = '.' then
217 -- Loop to scan digits of based number. On entry to the loop we
218 -- must have a valid digit. If we don't, then we have an illegal
219 -- floating-point value, and we raise Constraint_Error, note that
220 -- Ptr at this stage was reset to the proper (Start) value.
224 raise Constraint_Error
;
226 elsif Str
(P
) in Digs
then
227 Digit
:= Character'Pos (Str
(P
)) - Character'Pos ('0');
229 elsif Str
(P
) in 'A' .. 'F' then
231 Character'Pos (Str
(P
)) - (Character'Pos ('A') - 10);
233 elsif Str
(P
) in 'a' .. 'f' then
235 Character'Pos (Str
(P
)) - (Character'Pos ('a') - 10);
238 raise Constraint_Error
;
241 -- Save up trailing zeroes after the decimal point
243 if Digit
= 0 and After_Point
= 1 then
244 Num_Saved_Zeroes
:= Num_Saved_Zeroes
+ 1;
246 -- Here for a non-zero digit
249 -- First deal with any previously saved zeroes
251 if Num_Saved_Zeroes
/= 0 then
252 Uval
:= Uval
* Base
** Num_Saved_Zeroes
;
253 Scale
:= Scale
- Num_Saved_Zeroes
;
254 Num_Saved_Zeroes
:= 0;
257 -- Now accumulate the new digit
259 Fdigit
:= Long_Long_Float (Digit
);
261 if Fdigit
>= Base
then
264 Scale
:= Scale
- After_Point
;
265 Uval
:= Uval
* Base
+ Fdigit
;
272 raise Constraint_Error
;
274 elsif Str
(P
) = '_' then
275 Scan_Underscore
(Str
, P
, Ptr
, Max
, True);
278 -- Skip past period after digit. Note that the processing
279 -- here will permit either a digit after the period, or the
280 -- terminating base character, as allowed in (RM 3.5(48))
282 if Str
(P
) = '.' and then After_Point
= 0 then
287 raise Constraint_Error
;
291 exit when Str
(P
) = Base_Char
;
295 -- Based number successfully scanned out (point was found)
300 -- Non-based case, check for being at decimal point now. Note that
301 -- in Ada 95, we do not insist on a decimal point being present
307 if P
<= Max
and then Str
(P
) = '.' then
310 -- Scan digits after point if any are present (RM 3.5(46))
312 if P
<= Max
and then Str
(P
) in Digs
then
320 -- At this point, we have Uval containing the digits of the value as
321 -- an integer, and Scale indicates the negative of the number of digits
322 -- after the point. Base contains the base value (an integral value in
323 -- the range 2.0 .. 16.0). Test for exponent, must be at least one
324 -- character after the E for the exponent to be valid.
326 Scale
:= Scale
+ Scan_Exponent
(Str
, Ptr
, Max
, Real
=> True);
328 -- At this point the exponent has been scanned if one is present and
329 -- Scale is adjusted to include the exponent value. Uval contains the
330 -- the integral value which is to be multiplied by Base ** Scale.
332 -- If base is not 10, use exponentiation for scaling
335 Uval
:= Uval
* Base
** Scale
;
337 -- For base 10, use power of ten table, repeatedly if necessary
340 while Scale
> Maxpow
loop
341 Uval
:= Uval
* Powten
(Maxpow
);
342 Scale
:= Scale
- Maxpow
;
346 Uval
:= Uval
* Powten
(Scale
);
350 while (-Scale
) > Maxpow
loop
351 Uval
:= Uval
/ Powten
(Maxpow
);
352 Scale
:= Scale
+ Maxpow
;
356 Uval
:= Uval
/ Powten
(-Scale
);
360 -- Here is where we check for a bad based number
363 raise Constraint_Error
;
365 -- If OK, then deal with initial minus sign, note that this processing
366 -- is done even if Uval is zero, so that -0.0 is correctly interpreted.
381 function Value_Real
(Str
: String) return Long_Long_Float is
383 P
: aliased Integer := Str
'First;
385 V
:= Scan_Real
(Str
, P
'Access, Str
'Last);
386 Scan_Trailing_Blanks
(Str
, P
);