1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
|
------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S Y S T E M . V A L U E _ R --
-- --
-- S p e c --
-- --
-- Copyright (C) 2020-2024, 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 3, 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. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- This package contains routines for scanning real values for use in
-- Text_IO.Decimal_IO, Fixed_IO, Float_IO and the Value attribute.
with System.Unsigned_Types; use System.Unsigned_Types;
generic
type Uns is mod <>;
-- Modular type used for the value
Parts : Positive;
-- Number of Uns parts in the value
Precision_Limit : Uns;
-- Precision limit for each part of the value
Round : Boolean;
-- If Parts = 1, True if the extra digit must be rounded
package System.Value_R is
pragma Preelaborate;
subtype Data_Index is Positive range 1 .. Parts;
-- The type indexing the value
type Scale_Array is array (Data_Index) of Integer;
-- The scale for each part of the value
type Value_Array is array (Data_Index) of Uns;
-- The value split into parts
function Scan_Raw_Real
(Str : String;
Ptr : not null access Integer;
Max : Integer;
Base : out Unsigned;
Scale : out Scale_Array;
Extra : out Unsigned;
Minus : out Boolean) return Value_Array;
-- This function scans the string starting at Str (Ptr.all) for a valid
-- real literal according to the syntax described in (RM 3.5(43)). The
-- substring scanned extends no further than Str (Max). There are three
-- cases for the return:
--
-- If a valid real is found after scanning past any initial spaces, then
-- Ptr.all is updated past the last character of the real (but trailing
-- spaces are not scanned out) and the Base, Scale, Extra and Minus out
-- parameters are set; if Val is the result of the call, then the real
-- represented by the literal is equal to
--
-- (Val (1) * Base + Extra) * (Base ** (Scale (1) - 1))
--
-- when Parts = 1 and
--
-- Sum [Val (N) * (Base ** Scale (N)), N in 1 .. Parts]
--
-- when Parts > 1, with the negative sign if Minus is true.
--
-- If no valid real is found, then Ptr.all points either to an initial
-- non-blank character, or to Max + 1 if the field is all spaces and the
-- exception Constraint_Error is raised.
--
-- If a syntactically valid real is scanned, but the value is out of
-- range, or, in the based case, the base value is out of range or there
-- is an out of range digit, then Ptr.all points past the real literal,
-- and Constraint_Error is raised.
--
-- Note: these rules correspond to the requirements for leaving the
-- pointer positioned in Text_Io.Get
--
-- Note: if Str is null, i.e. if Max is less than Ptr, then this is a
-- special case of an all-blank string, and Ptr is unchanged, and hence
-- is greater than Max as required in this case.
--
-- Note: this routine should not be called with Str'Last = Positive'Last.
-- If this occurs Program_Error is raised with a message noting that this
-- case is not supported. Most such cases are eliminated by the caller.
function Value_Raw_Real
(Str : String;
Base : out Unsigned;
Scale : out Scale_Array;
Extra : out Unsigned;
Minus : out Boolean) return Value_Array;
-- Used in computing X'Value (Str) where X is a real type. Str is the
-- string argument of the attribute. Constraint_Error is raised if the
-- string is malformed.
end System.Value_R;
|
