File : s-valrea.adb
------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S Y S T E M . V A L _ R E A L --
-- --
-- S p e c --
-- --
-- $Revision: 1.16 $ --
-- --
-- Copyright (C) 1992-1998 Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 2, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
-- MA 02111-1307, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
-- --
------------------------------------------------------------------------------
with System.Powten_Table; use System.Powten_Table;
with System.Val_Util; use System.Val_Util;
package body System.Val_Real is
---------------
-- Scan_Real --
---------------
function Scan_Real
(Str : String;
Ptr : access Integer;
Max : Integer)
return Long_Long_Float
is
P : Integer;
-- Local copy of string pointer
Base : Long_Long_Float;
-- Base value
Uval : Long_Long_Float;
-- Accumulated float result
subtype Digs is Character range '0' .. '9';
-- Used to check for decimal digit
Scale : Integer := 0;
-- Power of Base to multiply result by
Start : Positive;
-- Position of starting non-blank character
Minus : Boolean;
-- Set to True if minus sign is present, otherwise to False
Bad_Base : Boolean := False;
-- Set True if Base out of range or if out of range digit
After_Point : Natural := 0;
-- Set to 1 after the point
procedure Scanf;
-- Scans integer literal value starting at current character position.
-- For each digit encountered, Uval is multiplied by 10.0, and the new
-- digit value is incremented. In addition Scale is decremented for each
-- digit encountered if we are after the point (After_Point = 1). The
-- longest possible syntactically valid numeral is scanned out, and on
-- return P points past the last character. On entry, the current
-- character is known to be a digit, so a numeral is definitely present.
procedure Scanf is
Digit : Natural;
begin
loop
Digit := Character'Pos (Str (P)) - Character'Pos ('0');
Uval := Uval * 10.0 + Long_Long_Float (Digit);
P := P + 1;
Scale := Scale - After_Point;
-- Done if end of input field
if P > Max then
return;
-- Check next character
elsif Str (P) not in Digs then
if Str (P) = '_' then
Scan_Underscore (Str, P, Ptr, Max, False);
else
return;
end if;
end if;
end loop;
end Scanf;
-- Start of processing for System.Scan_Real
begin
Scan_Sign (Str, Ptr, Max, Minus, Start);
P := Ptr.all;
Ptr.all := Start;
-- If digit, scan numeral before point
if Str (P) in Digs then
Uval := 0.0;
Scanf;
-- Initial point, allowed only if followed by digit (RM 3.5(47))
elsif Str (P) = '.'
and then P < Max
and then Str (P + 1) in Digs
then
Uval := 0.0;
-- Any other initial character is an error
else
raise Constraint_Error;
end if;
-- Deal with based case
if P < Max and then (Str (P) = ':' or else Str (P) = '#') then
declare
Base_Char : constant Character := Str (P);
Digit : Natural;
Fdigit : Long_Long_Float;
begin
-- Set bad base if out of range, and use safe base of 16.0,
-- to guard against division by zero in the loop below.
if Uval < 2.0 or else Uval > 16.0 then
Bad_Base := True;
Uval := 16.0;
end if;
Base := Uval;
Uval := 0.0;
P := P + 1;
-- Special check to allow initial point (RM 3.5(49))
if Str (P) = '.' then
After_Point := 1;
P := P + 1;
end if;
-- Loop to scan digits of based number. On entry to the loop we
-- must have a valid digit. If we don't, then we have an illegal
-- floating-point value, and we raise Constraint_Error, note that
-- Ptr at this stage was reset to the proper (Start) value.
loop
if P > Max then
raise Constraint_Error;
elsif Str (P) in Digs then
Digit := Character'Pos (Str (P)) - Character'Pos ('0');
elsif Str (P) in 'A' .. 'F' then
Digit :=
Character'Pos (Str (P)) - (Character'Pos ('A') - 10);
elsif Str (P) in 'a' .. 'f' then
Digit :=
Character'Pos (Str (P)) - (Character'Pos ('a') - 10);
else
raise Constraint_Error;
end if;
P := P + 1;
Fdigit := Long_Long_Float (Digit);
if Fdigit >= Base then
Bad_Base := True;
else
Scale := Scale - After_Point;
Uval := Uval * Base + Fdigit;
end if;
if P > Max then
raise Constraint_Error;
elsif Str (P) = '_' then
Scan_Underscore (Str, P, Ptr, Max, True);
else
-- Skip past period after digit. Note that the processing
-- here will permit either a digit after the period, or the
-- terminating base character, as allowed in (RM 3.5(48))
if Str (P) = '.' and then After_Point = 0 then
P := P + 1;
After_Point := 1;
if P > Max then
raise Constraint_Error;
end if;
end if;
exit when Str (P) = Base_Char;
end if;
end loop;
-- Based number successfully scanned out (point was found)
Ptr.all := P + 1;
end;
-- Non-based case, check for being at decimal point now. Note that
-- in Ada 95, we do not insist on a decimal point being present
else
Base := 10.0;
After_Point := 1;
if P <= Max and then Str (P) = '.' then
P := P + 1;
-- Scan digits after point if any are present (RM 3.5(46))
if P <= Max and then Str (P) in Digs then
Scanf;
end if;
end if;
Ptr.all := P;
end if;
-- At this point, we have Uval containing the digits of the value as
-- an integer, and Scale indicates the negative of the number of digits
-- after the point. Base contains the base value (an integral value in
-- the range 2.0 .. 16.0). Test for exponent, must be at least one
-- character after the E for the exponent to be valid.
Scale := Scale + Scan_Exponent (Str, Ptr, Max, Real => True);
-- At this point the exponent has been scanned if one is present and
-- Scale is adjusted to include the exponent value. Uval contains the
-- the integral value which is to be multiplied by Base ** Scale.
-- If base is not 10, use exponentiation for scaling
if Base /= 10.0 then
Uval := Uval * Base ** Scale;
-- For base 10, use power of ten table if in range
elsif Scale > 0 then
if Scale > Powten'Last then
Uval := Uval * 10.0 ** Scale;
else
Uval := Uval * Powten (Scale);
end if;
elsif Scale < 0 then
if (-Scale) > Powten'Last then
Uval := Uval * 10.0 ** Scale;
else
Uval := Uval / Powten (-Scale);
end if;
end if;
-- Here is where we check for a bad based number
if Bad_Base then
raise Constraint_Error;
-- If OK, then deal with initial minus sign, note that this processing
-- is done even if Uval is zero, so that -0.0 is correctly interpreted.
else
if Minus then
return -Uval;
else
return Uval;
end if;
end if;
end Scan_Real;
----------------
-- Value_Real --
----------------
function Value_Real (Str : String) return Long_Long_Float is
V : Long_Long_Float;
P : aliased Integer := Str'First;
begin
V := Scan_Real (Str, P'Access, Str'Last);
Scan_Trailing_Blanks (Str, P);
return V;
end Value_Real;
end System.Val_Real;