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Wrap

Text File | 1996-01-30 | 10KB | 323 lines

------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- S Y S T E M . V A L _ R E A L -- -- -- -- S p e c -- -- -- -- $Revision: 1.6 $ -- -- -- -- Copyright (c) 1992,1993,1994 NYU, All Rights Reserved -- -- -- -- The GNAT library is free software; you can redistribute it and/or modify -- -- it under terms of the GNU Library General Public License as published by -- -- the Free Software Foundation; either version 2, or (at your option) any -- -- later version. The GNAT library is distributed in the hope that it will -- -- be useful, but WITHOUT ANY WARRANTY; without even the implied warranty -- -- of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU -- -- Library General Public License for more details. You should have -- -- received a copy of the GNU Library General Public License along with -- -- the GNAT library; see the file COPYING.LIB. If not, write to the Free -- -- Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. -- -- -- ------------------------------------------------------------------------------ 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 Positive'Base; Max : Positive'Base) return Long_Long_Float is P : Positive'Base; -- 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; -- Non-digit encountered elsif Str (P) not in Digs then -- If syntactically valid underline, just skip it if Str (P) = '_' and then P < Max and then Str (P + 1) in Digs then P := P + 1; -- If any other non-digit, return 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 if Uval < 2.0 or else Uval > 16.0 then Bad_Base := True; 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; -- Error if no base character after digit scanned if P > Max then raise Constraint_Error; -- Just skip past underline (we will require digit after it) elsif Str (P) = '_' then P := P + 1; 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; -- Terminating base character is recognized only if it -- appears after a point, otherwise it is illegal exit when Str (P) = Base_Char and then After_Point = 1; end if; end loop; -- Based number successfully scanned out (point was found) Ptr.all := P + 1; end; -- Non-based case, we must be at a point now else if Str (P) /= '.' then raise Constraint_Error; else Base := 10.0; After_Point := 1; 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; Ptr.all := P; end if; 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'Length then Uval := Uval * 10.0 ** Scale; else Uval := Uval * Powten (Scale); end if; elsif Scale < 0 then if (-Scale) > Powten'Length 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 Natural := 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;