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1 | [/ |
2 | Boost.Optional | |
3 | ||
4 | Copyright (c) 2003-2007 Fernando Luis Cacciola Carballal | |
5 | ||
6 | Distributed under the Boost Software License, Version 1.0. | |
7 | (See accompanying file LICENSE_1_0.txt or copy at | |
8 | http://www.boost.org/LICENSE_1_0.txt) | |
9 | ] | |
10 | ||
11 | [section bounds<> traits class] | |
12 | ||
13 | [section Introduction] | |
14 | ||
15 | To determine the ranges of numeric types with `std::numeric_limits` \[18.2.1\], | |
16 | different syntax have to be used depending on numeric type. Specifically, | |
17 | `numeric_limits<T>::min()` for integral types returns the minimum finite value, | |
18 | whereas for floating point types it returns the minimum positive normalized | |
19 | value. The difference in semantics makes client code unnecessarily complex | |
20 | and error prone. | |
21 | ||
22 | `boost::numeric::bounds<>` provides a consistent interface for retrieving the | |
23 | maximum finite value, the minimum finite value and the minimum positive normalized | |
24 | value (0 for integral types) for numeric types. The selection of implementation | |
25 | is performed at compile time, so there is no runtime overhead. | |
26 | ||
27 | [endsect] | |
28 | ||
29 | [section traits class bounds<N>] | |
30 | ||
31 | template<class N> | |
32 | struct bounds | |
33 | { | |
34 | static N lowest () { return implementation_defined; } | |
35 | static N highest () { return implementation_defined; } | |
36 | static N smallest() { return implementation_defined; } | |
37 | }; | |
38 | ||
39 | [heading Members] | |
40 | ||
41 | ||
42 | [: `lowest()` ] | |
43 | ||
44 | Returns the minimum finite value, equivalent to `numeric_limits<T>::min()` when `T` | |
45 | is an integral type, and to `-numeric_limits<T>::max()` when `T` is a floating point type. | |
46 | ||
47 | [: `highest()` ] | |
48 | ||
49 | Returns the maximum finite value, equivalent to `numeric_limits<T>::max()`. | |
50 | ||
51 | [: `smallest()` ] | |
52 | ||
53 | Returns the smallest positive normalized value for floating point types with | |
54 | denormalization, or returns 0 for integral types. | |
55 | ||
56 | [endsect] | |
57 | ||
58 | [section Examples] | |
59 | ||
60 | The following example demonstrates the use of `numeric::bounds<>` and the | |
61 | equivalent code using `numeric_limits`: | |
62 | ||
63 | #include <iostream> | |
64 | ||
65 | #include <boost/numeric/conversion/bounds.hpp> | |
66 | #include <boost/limits.hpp> | |
67 | ||
68 | int main() { | |
69 | ||
70 | std::cout << "numeric::bounds versus numeric_limits example.\n"; | |
71 | ||
72 | std::cout << "The maximum value for float:\n"; | |
73 | std::cout << boost::numeric::bounds<float>::highest() << "\n"; | |
74 | std::cout << std::numeric_limits<float>::max() << "\n"; | |
75 | ||
76 | std::cout << "The minimum value for float:\n"; | |
77 | std::cout << boost::numeric::bounds<float>::lowest() << "\n"; | |
78 | std::cout << -std::numeric_limits<float>::max() << "\n"; | |
79 | ||
80 | std::cout << "The smallest positive value for float:\n"; | |
81 | std::cout << boost::numeric::bounds<float>::smallest() << "\n"; | |
82 | std::cout << std::numeric_limits<float>::min() << "\n"; | |
83 | ||
84 | return 0; | |
85 | } | |
86 | ||
87 | ||
88 | [endsect] | |
89 | ||
90 | [endsect] | |
91 | ||
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100 |