gcc/ada/libgnat/s-valrea.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                      S Y S T E M . V A L _ R E A L                       --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2024, Free Software Foundation, Inc.         --
  10 --                                                                          --
  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.                                     --
  17 --                                                                          --
  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.               --
  21 --                                                                          --
  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/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 --  This package contains routines for scanning real values for use in
  33 --  Text_IO.Float_IO and the Value attribute.
  34
  35 generic
  36
  37    type Num is digits <>;
  38
  39    Maxpow : Positive;
  40
  41    Powfive_Address : System.Address;
  42
  43    Powfive_100_Address : System.Address;
  44
  45    Powfive_200_Address : System.Address;
  46
  47    Powfive_300_Address : System.Address;
  48
  49    type Uns is mod <>;
  50
  51 package System.Val_Real is
  52    pragma Preelaborate;
  53
  54    function Scan_Real
  55      (Str : String;
  56       Ptr : not null access Integer;
  57       Max : Integer) return Num;
  58    --  This function scans the string starting at Str (Ptr.all) for a valid
  59    --  real literal according to the syntax described in (RM 3.5(43)). The
  60    --  substring scanned extends no further than Str (Max). There are three
  61    --  cases for the return:
  62    --
  63    --  If a valid real is found after scanning past any initial spaces, then
  64    --  Ptr.all is updated past the last character of the real (but trailing
  65    --  spaces are not scanned out).
  66    --
  67    --  If no valid real is found, then Ptr.all points either to an initial
  68    --  non-blank character, or to Max + 1 if the field is all spaces and the
  69    --  exception Constraint_Error is raised.
  70    --
  71    --  If a syntactically valid real is scanned, but the value is out of
  72    --  range, or, in the based case, the base value is out of range or there
  73    --  is an out of range digit, then Ptr.all points past the real literal,
  74    --  and Constraint_Error is raised.
  75    --
  76    --  Note: these rules correspond to the requirements for leaving the
  77    --  pointer positioned in Text_Io.Get
  78    --
  79    --  Note: if Str is null, i.e. if Max is less than Ptr, then this is a
  80    --  special case of an all-blank string, and Ptr is unchanged, and hence
  81    --  is greater than Max as required in this case.
  82    --
  83    --  Note: this routine should not be called with Str'Last = Positive'Last.
  84    --  If this occurs Program_Error is raised with a message noting that this
  85    --  case is not supported. Most such cases are eliminated by the caller.
  86
  87    function Value_Real (Str : String) return Num;
  88    --  Used in computing X'Value (Str) where X is a floating-point type or an
  89    --  ordinary fixed-point type. Str is the string argument of the attribute.
  90    --  Constraint_Error is raised if the string is malformed, or if the value
  91    --  out of range of Num.
  92
  93 end System.Val_Real;