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.
92 procedure Bad_Based_Value
;
93 pragma No_Return
(Bad_Based_Value
);
94 -- Raise exception for bad based value
97 -- Scans integer literal value starting at current character position.
98 -- For each digit encountered, Uval is multiplied by 10.0, and the new
99 -- digit value is incremented. In addition Scale is decremented for each
100 -- digit encountered if we are after the point (After_Point = 1). The
101 -- longest possible syntactically valid numeral is scanned out, and on
102 -- return P points past the last character. On entry, the current
103 -- character is known to be a digit, so a numeral is definitely present.
105 ---------------------
106 -- Bad_Based_Value --
107 ---------------------
109 procedure Bad_Based_Value
is
111 raise Constraint_Error
with
112 "invalid based literal for 'Value";
124 Digit
:= Character'Pos (Str
(P
)) - Character'Pos ('0');
127 -- Save up trailing zeroes after the decimal point
129 if Digit
= 0 and then After_Point
= 1 then
130 Num_Saved_Zeroes
:= Num_Saved_Zeroes
+ 1;
132 -- Here for a non-zero digit
135 -- First deal with any previously saved zeroes
137 if Num_Saved_Zeroes
/= 0 then
138 while Num_Saved_Zeroes
> Maxpow
loop
139 Uval
:= Uval
* Powten
(Maxpow
);
140 Num_Saved_Zeroes
:= Num_Saved_Zeroes
- Maxpow
;
141 Scale
:= Scale
- Maxpow
;
144 Uval
:= Uval
* Powten
(Num_Saved_Zeroes
);
145 Scale
:= Scale
- Num_Saved_Zeroes
;
147 Num_Saved_Zeroes
:= 0;
150 -- Accumulate new digit
152 Uval
:= Uval
* 10.0 + Long_Long_Float (Digit
);
153 Scale
:= Scale
- After_Point
;
156 -- Done if end of input field
161 -- Check next character
163 elsif Str
(P
) not in Digs
then
164 if Str
(P
) = '_' then
165 Scan_Underscore
(Str
, P
, Ptr
, Max
, False);
173 -- Start of processing for System.Scan_Real
177 Scan_Sign
(Str
, Ptr
, Max
, Minus
, Start
);
181 -- If digit, scan numeral before point
183 if Str
(P
) in Digs
then
187 -- Initial point, allowed only if followed by digit (RM 3.5(47))
191 and then Str
(P
+ 1) in Digs
195 -- Any other initial character is an error
198 raise Constraint_Error
with
199 "invalid character in 'Value string";
202 -- Deal with based case
204 if P
< Max
and then (Str
(P
) = ':' or else Str
(P
) = '#') then
206 Base_Char
: constant Character := Str
(P
);
208 Fdigit
: Long_Long_Float;
211 -- Set bad base if out of range, and use safe base of 16.0,
212 -- to guard against division by zero in the loop below.
214 if Uval
< 2.0 or else Uval
> 16.0 then
223 -- Special check to allow initial point (RM 3.5(49))
225 if Str
(P
) = '.' then
230 -- Loop to scan digits of based number. On entry to the loop we
231 -- must have a valid digit. If we don't, then we have an illegal
232 -- floating-point value, and we raise Constraint_Error, note that
233 -- Ptr at this stage was reset to the proper (Start) value.
239 elsif Str
(P
) in Digs
then
240 Digit
:= Character'Pos (Str
(P
)) - Character'Pos ('0');
242 elsif Str
(P
) in 'A' .. 'F' then
244 Character'Pos (Str
(P
)) - (Character'Pos ('A') - 10);
246 elsif Str
(P
) in 'a' .. 'f' then
248 Character'Pos (Str
(P
)) - (Character'Pos ('a') - 10);
254 -- Save up trailing zeroes after the decimal point
256 if Digit
= 0 and then After_Point
= 1 then
257 Num_Saved_Zeroes
:= Num_Saved_Zeroes
+ 1;
259 -- Here for a non-zero digit
262 -- First deal with any previously saved zeroes
264 if Num_Saved_Zeroes
/= 0 then
265 Uval
:= Uval
* Base
** Num_Saved_Zeroes
;
266 Scale
:= Scale
- Num_Saved_Zeroes
;
267 Num_Saved_Zeroes
:= 0;
270 -- Now accumulate the new digit
272 Fdigit
:= Long_Long_Float (Digit
);
274 if Fdigit
>= Base
then
277 Scale
:= Scale
- After_Point
;
278 Uval
:= Uval
* Base
+ Fdigit
;
287 elsif Str
(P
) = '_' then
288 Scan_Underscore
(Str
, P
, Ptr
, Max
, True);
291 -- Skip past period after digit. Note that the processing
292 -- here will permit either a digit after the period, or the
293 -- terminating base character, as allowed in (RM 3.5(48))
295 if Str
(P
) = '.' and then After_Point
= 0 then
304 exit when Str
(P
) = Base_Char
;
308 -- Based number successfully scanned out (point was found)
313 -- Non-based case, check for being at decimal point now. Note that
314 -- in Ada 95, we do not insist on a decimal point being present
320 if P
<= Max
and then Str
(P
) = '.' then
323 -- Scan digits after point if any are present (RM 3.5(46))
325 if P
<= Max
and then Str
(P
) in Digs
then
333 -- At this point, we have Uval containing the digits of the value as
334 -- an integer, and Scale indicates the negative of the number of digits
335 -- after the point. Base contains the base value (an integral value in
336 -- the range 2.0 .. 16.0). Test for exponent, must be at least one
337 -- character after the E for the exponent to be valid.
339 Scale
:= Scale
+ Scan_Exponent
(Str
, Ptr
, Max
, Real
=> True);
341 -- At this point the exponent has been scanned if one is present and
342 -- Scale is adjusted to include the exponent value. Uval contains the
343 -- the integral value which is to be multiplied by Base ** Scale.
345 -- If base is not 10, use exponentiation for scaling
348 Uval
:= Uval
* Base
** Scale
;
350 -- For base 10, use power of ten table, repeatedly if necessary
353 while Scale
> Maxpow
loop
354 Uval
:= Uval
* Powten
(Maxpow
);
355 Scale
:= Scale
- Maxpow
;
359 Uval
:= Uval
* Powten
(Scale
);
363 while (-Scale
) > Maxpow
loop
364 Uval
:= Uval
/ Powten
(Maxpow
);
365 Scale
:= Scale
+ Maxpow
;
369 Uval
:= Uval
/ Powten
(-Scale
);
373 -- Here is where we check for a bad based number
378 -- If OK, then deal with initial minus sign, note that this processing
379 -- is done even if Uval is zero, so that -0.0 is correctly interpreted.
394 function Value_Real
(Str
: String) return Long_Long_Float is
396 P
: aliased Integer := Str
'First;
398 V
:= Scan_Real
(Str
, P
'Access, Str
'Last);
399 Scan_Trailing_Blanks
(Str
, P
);