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1 | /* Nelper routines to convert from integer to real. |
2 | Copyright 2004 Free Software Foundation, Inc. | |
3 | Contributed by Paul Brook. | |
4 | ||
5 | This file is part of the GNU Fortran 95 runtime library (libgfortran). | |
6 | ||
7 | Libgfortran is free software; you can redistribute it and/or | |
57dea9f6 | 8 | modify it under the terms of the GNU General Public |
a9e7b9d3 | 9 | License as published by the Free Software Foundation; either |
57dea9f6 TM |
10 | version 2 of the License, or (at your option) any later version. |
11 | ||
12 | In addition to the permissions in the GNU General Public License, the | |
13 | Free Software Foundation gives you unlimited permission to link the | |
14 | compiled version of this file into combinations with other programs, | |
15 | and to distribute those combinations without any restriction coming | |
16 | from the use of this file. (The General Public License restrictions | |
17 | do apply in other respects; for example, they cover modification of | |
18 | the file, and distribution when not linked into a combine | |
19 | executable.) | |
a9e7b9d3 PB |
20 | |
21 | Ligbfortran is distributed in the hope that it will be useful, | |
22 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
23 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
57dea9f6 | 24 | GNU General Public License for more details. |
a9e7b9d3 | 25 | |
57dea9f6 TM |
26 | You should have received a copy of the GNU General Public |
27 | License along with libgfortran; see the file COPYING. If not, | |
a9e7b9d3 PB |
28 | write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, |
29 | Boston, MA 02111-1307, USA. */ | |
30 | #include <math.h> | |
31 | #include "libgfortran.h" | |
32 | ||
33 | /* These routines can be sensitive to excess precision, so should really be | |
34 | compiled with -ffloat-store. */ | |
35 | ||
36 | /* Return the largest value less than one representable in a REAL*4. */ | |
37 | ||
38 | static inline GFC_REAL_4 | |
39 | almostone_r4 () | |
40 | { | |
41 | #ifdef HAVE_NEXTAFTERF | |
42 | return nextafterf (1.0f, 0.0f); | |
43 | #else | |
44 | /* The volatile is a hack to prevent excess precision on x86. */ | |
45 | static volatile GFC_REAL_4 val = 0.0f; | |
46 | GFC_REAL_4 x; | |
47 | ||
48 | if (val != 0.0f) | |
49 | return val; | |
50 | ||
51 | val = 0.9999f; | |
52 | do | |
53 | { | |
54 | x = val; | |
55 | val = (val + 1.0f) / 2.0f; | |
56 | } | |
57 | while (val > x && val < 1.0f); | |
58 | if (val == 1.0f) | |
59 | val = x; | |
60 | return val; | |
61 | #endif | |
62 | } | |
63 | ||
64 | ||
65 | /* Return the largest value less than one representable in a REAL*8. */ | |
66 | ||
67 | static inline GFC_REAL_8 | |
68 | almostone_r8 () | |
69 | { | |
70 | #ifdef HAVE_NEXTAFTER | |
71 | return nextafter (1.0, 0.0); | |
72 | #else | |
73 | static volatile GFC_REAL_8 val = 0.0; | |
74 | GFC_REAL_8 x; | |
75 | ||
76 | if (val != 0.0) | |
77 | return val; | |
78 | ||
79 | val = 0.9999; | |
80 | do | |
81 | { | |
82 | x = val; | |
83 | val = (val + 1.0) / 2.0; | |
84 | } | |
85 | while (val > x && val < 1.0); | |
86 | if (val == 1.0) | |
87 | val = x; | |
88 | return val; | |
89 | #endif | |
90 | } | |
91 | ||
92 | ||
beabab59 | 93 | /* Convert an unsigned integer in the range [0..x] into a |
a9e7b9d3 PB |
94 | real the range [0..1). */ |
95 | ||
96 | GFC_REAL_4 | |
97 | normalize_r4_i4 (GFC_UINTEGER_4 i, GFC_UINTEGER_4 x) | |
98 | { | |
99 | GFC_REAL_4 r; | |
100 | ||
101 | r = (GFC_REAL_4) i / (GFC_REAL_4) x; | |
102 | if (r == 1.0f) | |
103 | r = almostone_r4 (); | |
104 | return r; | |
105 | } | |
106 | ||
107 | ||
beabab59 | 108 | /* Convert an unsigned integer in the range [0..x] into a |
a9e7b9d3 PB |
109 | real the range [0..1). */ |
110 | ||
111 | GFC_REAL_8 | |
112 | normalize_r8_i8 (GFC_UINTEGER_8 i, GFC_UINTEGER_8 x) | |
113 | { | |
114 | GFC_REAL_8 r; | |
115 | ||
116 | r = (GFC_REAL_8) i / (GFC_REAL_8) x; | |
117 | if (r == 1.0) | |
118 | r = almostone_r8 (); | |
119 | return r; | |
120 | } |