ceph/src/boost/libs/numeric/conversion/doc/bounds.qbk

   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]
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