| 1 | <html> |
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| 2 | <head> |
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| 3 | <title>The Boost Tuple Library</title> |
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| 4 | </head> |
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| 5 | <body bgcolor="#FFFFFF" text="#000000"> |
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| 6 | |
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| 7 | <IMG SRC="../../../boost.png" |
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| 8 | ALT="C++ Boost" width="277" height="86"> |
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| 9 | |
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| 10 | <h1>The Boost Tuple Library</h1> |
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| 11 | |
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| 12 | <p> |
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| 13 | A tuple (or <i>n</i>-tuple) is a fixed size collection of elements. |
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| 14 | Pairs, triples, quadruples etc. are tuples. |
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| 15 | In a programming language, a tuple is a data object containing other objects as elements. |
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| 16 | These element objects may be of different types. |
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| 17 | </p> |
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| 18 | |
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| 19 | <p>Tuples are convenient in many circumstances. |
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| 20 | For instance, tuples make it easy to define functions that return more than one value. |
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| 21 | </p> |
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| 22 | |
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| 23 | <p> |
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| 24 | Some programming languages, such as ML, Python and Haskell, have built-in tuple constructs. |
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| 25 | Unfortunately C++ does not. |
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| 26 | To compensate for this "deficiency", the Boost Tuple Library implements a tuple construct using templates. |
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| 27 | </p> |
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| 28 | |
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| 29 | <h2>Table of Contents</h2> |
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| 30 | |
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| 31 | <ol> |
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| 32 | <li><a href = "#using_library">Using the library</a></li> |
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| 33 | <li><a href = "#tuple_types">Tuple types</a></li> |
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| 34 | <li><a href = "#constructing_tuples">Constructing tuples</a></li> |
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| 35 | <li><a href = "#accessing_elements">Accessing tuple elements</a></li> |
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| 36 | <li><a href = "#construction_and_assignment">Copy construction and tuple assignment</a></li> |
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| 37 | <li><a href = "#relational_operators">Relational operators</a></li> |
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| 38 | <li><a href = "#tiers">Tiers</a></li> |
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| 39 | <li><a href = "#streaming">Streaming</a></li> |
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| 40 | <li><a href = "#performance">Performance</a></li> |
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| 41 | <li><a href = "#portability">Portability</a></li> |
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| 42 | <li><a href = "#thanks">Acknowledgements</a></li> |
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| 43 | <li><a href = "#references">References</a></li> |
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| 44 | </ol> |
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| 45 | |
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| 46 | <h4>More details</h4> |
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| 47 | |
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| 48 | <p> |
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| 49 | <a href = "tuple_advanced_interface.html">Advanced features</a> (describes some metafunctions etc.).</p> |
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| 50 | <p> |
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| 51 | <a href = "design_decisions_rationale.html">Rationale behind some design/implementation decisions.</a></p> |
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| 52 | |
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| 53 | |
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| 54 | <h2><a name="using_library">Using the library</a></h2> |
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| 55 | |
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| 56 | <p>To use the library, just include: |
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| 57 | |
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| 58 | <pre><code>#include "boost/tuple/tuple.hpp"</code></pre> |
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| 59 | |
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| 60 | <p>Comparison operators can be included with: |
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| 61 | <pre><code>#include "boost/tuple/tuple_comparison.hpp"</code></pre> |
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| 62 | |
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| 63 | <p>To use tuple input and output operators, |
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| 64 | |
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| 65 | <pre><code>#include "boost/tuple/tuple_io.hpp"</code></pre> |
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| 66 | |
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| 67 | Both <code>tuple_io.hpp</code> and <code>tuple_comparison.hpp</code> include <code>tuple.hpp</code>. |
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| 68 | |
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| 69 | <p>All definitions are in namespace <code>::boost::tuples</code>, but the most common names are lifted to namespace <code>::boost</code> with using declarations. These names are: <code>tuple</code>, <code>make_tuple</code>, <code>tie</code> and <code>get</code>. Further, <code>ref</code> and <code>cref</code> are defined directly under the <code>::boost</code> namespace. |
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| 70 | |
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| 71 | <h2><a name = "tuple_types">Tuple types</a></h2> |
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| 72 | |
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| 73 | <p>A tuple type is an instantiation of the <code>tuple</code> template. |
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| 74 | The template parameters specify the types of the tuple elements. |
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| 75 | The current version supports tuples with 0-10 elements. |
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| 76 | If necessary, the upper limit can be increased up to, say, a few dozen elements. |
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| 77 | The data element can be any C++ type. |
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| 78 | Note that <code>void</code> and plain function types are valid |
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| 79 | C++ types, but objects of such types cannot exist. |
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| 80 | Hence, if a tuple type contains such types as elements, the tuple type |
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| 81 | can exist, but not an object of that type. |
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| 82 | There are natural limitations for element types that cannot |
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| 83 | be be copied, or that are not default constructible (see 'Constructing tuples' |
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| 84 | below). |
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| 85 | |
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| 86 | <p> |
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| 87 | For example, the following definitions are valid tuple instantiations (<code>A</code>, <code>B</code> and <code>C</code> are some user defined classes): |
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| 88 | |
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| 89 | <pre><code>tuple<int> |
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| 90 | tuple<double&, const double&, const double, double*, const double*> |
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| 91 | tuple<A, int(*)(char, int), B(A::*)(C&), C> |
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| 92 | tuple<std::string, std::pair<A, B> > |
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| 93 | tuple<A*, tuple<const A*, const B&, C>, bool, void*> |
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| 94 | </code></pre> |
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| 95 | |
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| 96 | <h2><a name = "constructing_tuples">Constructing tuples</a></h2> |
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| 97 | |
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| 98 | <p> |
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| 99 | The tuple constructor takes the tuple elements as arguments. |
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| 100 | For an <i>n</i>-element tuple, the constructor can be invoked with <i>k</i> arguments, where 0 <= <i>k</i> <= <i>n</i>. |
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| 101 | For example: |
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| 102 | <pre><code>tuple<int, double>() |
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| 103 | tuple<int, double>(1) |
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| 104 | tuple<int, double>(1, 3.14) |
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| 105 | </code></pre> |
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| 106 | |
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| 107 | <p> |
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| 108 | If no initial value for an element is provided, it is default initialized (and hence must be default initializable). |
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| 109 | For example. |
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| 110 | |
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| 111 | <pre><code>class X { |
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| 112 | X(); |
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| 113 | public: |
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| 114 | X(std::string); |
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| 115 | }; |
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| 116 | |
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| 117 | tuple<X,X,X>() // error: no default constructor for X |
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| 118 | tuple<X,X,X>(string("Jaba"), string("Daba"), string("Duu")) // ok |
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| 119 | </code></pre> |
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| 120 | |
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| 121 | In particular, reference types do not have a default initialization: |
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| 122 | |
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| 123 | <pre><code>tuple<double&>() // error: reference must be |
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| 124 | // initialized explicitly |
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| 125 | |
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| 126 | double d = 5; |
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| 127 | tuple<double&>(d) // ok |
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| 128 | |
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| 129 | tuple<double&>(d+3.14) // error: cannot initialize |
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| 130 | // non-const reference with a temporary |
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| 131 | |
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| 132 | tuple<const double&>(d+3.14) // ok, but dangerous: |
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| 133 | // the element becomes a dangling reference |
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| 134 | </code></pre> |
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| 135 | |
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| 136 | <p>Using an initial value for an element that cannot be copied, is a compile |
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| 137 | time error: |
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| 138 | |
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| 139 | <pre><code>class Y { |
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| 140 | Y(const Y&); |
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| 141 | public: |
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| 142 | Y(); |
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| 143 | }; |
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| 144 | |
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| 145 | char a[10]; |
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| 146 | |
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| 147 | tuple<char[10], Y>(a, Y()); // error, neither arrays nor Y can be copied |
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| 148 | tuple<char[10], Y>(); // ok |
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| 149 | </code></pre> |
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| 150 | |
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| 151 | Note particularly that the following is perfectly ok: |
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| 152 | <code><pre>Y y; |
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| 153 | tuple<char(&)[10], Y&>(a, y); |
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| 154 | </code></pre> |
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| 155 | |
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| 156 | It is possible to come up with a tuple type that cannot be constructed. |
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| 157 | This occurs if an element that cannot be initialized has a lower |
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| 158 | index than an element that requires initialization. |
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| 159 | For example: <code>tuple<char[10], int&></code>. |
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| 160 | |
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| 161 | <p>In sum, the tuple construction is semantically just a group of individual elementary constructions. |
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| 162 | </p> |
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| 163 | |
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| 164 | <h4><a name="make_tuple">The <code>make_tuple</code> function</a></h4> |
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| 165 | |
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| 166 | <p> |
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| 167 | Tuples can also be constructed using the <code>make_tuple</code> (cf. <code>std::make_pair</code>) helper functions. |
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| 168 | This makes the construction more convenient, saving the programmer from explicitly specifying the element types: |
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| 169 | <pre><code>tuple<int, int, double> add_multiply_divide(int a, int b) { |
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| 170 | return make_tuple(a+b, a*b, double(a)/double(b)); |
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| 171 | } |
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| 172 | </code></pre> |
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| 173 | |
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| 174 | <p> |
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| 175 | By default, the element types are deduced to the plain non-reference types. E.g: |
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| 176 | <pre><code>void foo(const A& a, B& b) { |
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| 177 | ... |
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| 178 | make_tuple(a, b); |
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| 179 | </code></pre> |
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| 180 | The <code>make_tuple</code> invocation results in a tuple of type <code>tuple<A, B></code>. |
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| 181 | |
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| 182 | <p> |
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| 183 | Sometimes the plain non-reference type is not desired, e.g. if the element type cannot be copied. |
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| 184 | Therefore, the programmer can control the type deduction and state that a reference to const or reference to |
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| 185 | non-const type should be used as the element type instead. |
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| 186 | This is accomplished with two helper template functions: <code>ref</code> and <code>cref</code>. |
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| 187 | Any argument can be wrapped with these functions to get the desired type. |
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| 188 | The mechanism does not compromise const correctness since a const object wrapped with <code>ref</code> results in a tuple element with const reference type (see the fifth code line below). |
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| 189 | For example: |
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| 190 | |
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| 191 | <pre><code>A a; B b; const A ca = a; |
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| 192 | make_tuple(cref(a), b); // creates tuple<const A&, B> |
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| 193 | make_tuple(ref(a), b); // creates tuple<A&, B> |
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| 194 | make_tuple(ref(a), cref(b)); // creates tuple<A&, const B&> |
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| 195 | make_tuple(cref(ca)); // creates tuple<const A&> |
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| 196 | make_tuple(ref(ca)); // creates tuple<const A&> |
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| 197 | </code></pre> |
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| 198 | |
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| 199 | |
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| 200 | <p> |
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| 201 | Array arguments to <code>make_tuple</code> functions are deduced to reference to const types by default; there is no need to wrap them with <code>cref</code>. For example: |
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| 202 | <pre><code>make_tuple("Donald", "Daisy"); |
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| 203 | </code></pre> |
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| 204 | |
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| 205 | This creates an object of type <code>tuple<const char (&)[7], const char (&)[6]></code> |
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| 206 | (note that the type of a string literal is an array of const characters, not <code>const char*</code>). |
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| 207 | However, to get <code>make_tuple</code> to create a tuple with an element of a |
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| 208 | non-const array type one must use the <code>ref</code> wrapper. |
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| 209 | |
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| 210 | <p> |
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| 211 | Function pointers are deduced to the plain non-reference type, that is, to plain function pointer. |
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| 212 | A tuple can also hold a reference to a function, |
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| 213 | but such a tuple cannot be constructed with <code>make_tuple</code> (a const qualified function type would result, which is illegal): |
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| 214 | <pre><code>void f(int i); |
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| 215 | ... |
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| 216 | make_tuple(&f); // tuple<void (*)(int)> |
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| 217 | ... |
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| 218 | tuple<tuple<void (&)(int)> > a(f) // ok |
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| 219 | make_tuple(f); // not ok |
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| 220 | </code></pre> |
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| 221 | |
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| 222 | <h2><a name = "accessing_elements">Accessing tuple elements</a></h2> |
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| 223 | |
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| 224 | <p> |
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| 225 | Tuple elements are accessed with the expression: |
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| 226 | |
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| 227 | <pre><code>t.get<N>() |
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| 228 | </code></pre> |
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| 229 | or |
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| 230 | <pre><code>get<N>(t) |
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| 231 | </code></pre> |
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| 232 | where <code>t</code> is a tuple object and <code>N</code> is a constant integral expression specifying the index of the element to be accessed. |
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| 233 | Depending on whether <code>t</code> is const or not, <code>get</code> returns the <code>N</code>th element as a reference to const or |
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| 234 | non-const type. |
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| 235 | The index of the first element is 0 and thus<code> |
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| 236 | N</code> must be between 0 and <code>k-1</code>, where <code>k</code> is the number of elements in the tuple. |
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| 237 | Violations of these constrains are detected at compile time. Examples: |
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| 238 | |
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| 239 | <pre><code>double d = 2.7; A a; |
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| 240 | tuple<int, double&, const A&> t(1, d, a); |
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| 241 | const tuple<int, double&, const A&> ct = t; |
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| 242 | ... |
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| 243 | int i = get<0>(t); i = t.get<0>(); // ok |
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| 244 | int j = get<0>(ct); // ok |
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| 245 | get<0>(t) = 5; // ok |
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| 246 | get<0>(ct) = 5; // error, can't assign to const |
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| 247 | ... |
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| 248 | double e = get<1>(t); // ok |
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| 249 | get<1>(t) = 3.14; // ok |
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| 250 | get<2>(t) = A(); // error, can't assign to const |
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| 251 | A aa = get<3>(t); // error: index out of bounds |
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| 252 | ... |
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| 253 | ++get<0>(t); // ok, can be used as any variable |
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| 254 | </code></pre> |
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| 255 | |
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| 256 | Note! The member get functions are not supported with MS Visual C++ compiler. |
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| 257 | Further, the compiler has trouble with finding the non-member get functions without an explicit namespace qualifier. |
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| 258 | Hence, all <code>get</code> calls should be qualified as: <code>tuples::get<N>(a_tuple)</code> when writing code that shoud compile with MSVC++ 6.0. |
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| 259 | |
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| 260 | <h2><a name = "construction_and_assignment">Copy construction and tuple assignment</a></h2> |
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| 261 | |
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| 262 | <p> |
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| 263 | A tuple can be copy constructed from another tuple, provided that the element types are element-wise copy constructible. |
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| 264 | Analogously, a tuple can be assigned to another tuple, provided that the element types are element-wise assignable. |
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| 265 | For example: |
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| 266 | |
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| 267 | <pre><code>class A {}; |
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| 268 | class B : public A {}; |
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| 269 | struct C { C(); C(const B&); }; |
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| 270 | struct D { operator C() const; }; |
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| 271 | tuple<char, B*, B, D> t; |
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| 272 | ... |
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| 273 | tuple<int, A*, C, C> a(t); // ok |
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| 274 | a = t; // ok |
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| 275 | </code></pre> |
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| 276 | |
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| 277 | In both cases, the conversions performed are: <code>char -> int</code>, <code>B* -> A*</code> (derived class pointer to base class pointer), <code>B -> C</code> (a user defined conversion) and <code>D -> C</code> (a user defined conversion). |
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| 278 | |
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| 279 | <p> |
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| 280 | Note that assignment is also defined from <code>std::pair</code> types: |
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| 281 | |
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| 282 | <pre><code>tuple<float, int> a = std::make_pair(1, 'a'); |
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| 283 | </code></pre> |
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| 284 | |
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| 285 | <h2><a name = "relational_operators">Relational operators</a></h2> |
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| 286 | <p> |
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| 287 | Tuples reduce the operators <code>==, !=, <, >, <=</code> and <code>>=</code> to the corresponding elementary operators. |
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| 288 | This means, that if any of these operators is defined between all elements of two tuples, then the same operator is defined between the tuples as well. |
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| 289 | |
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| 290 | The equality operators for two tuples <code>a</code> and <code>b</code> are defined as: |
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| 291 | <ul> |
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| 292 | <li><code>a == b</code> iff for each <code>i</code>: <code>a<sub>i</sub> == b<sub>i</sub></code></li> |
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| 293 | <li><code>a != b</code> iff exists <code>i</code>: <code>a<sub>i</sub> != b<sub>i</sub></code></li> |
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| 294 | </ul> |
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| 295 | |
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| 296 | The operators <code><, >, <=</code> and <code>>=</code> implement a lexicographical ordering. |
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| 297 | |
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| 298 | <p> |
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| 299 | Note that an attempt to compare two tuples of different lengths results in a compile time error.</p> |
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| 300 | Also, the comparison operators are <i>"short-circuited"</i>: elementary comparisons start from the first elements and are performed only until the result is clear. |
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| 301 | |
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| 302 | <p>Examples: |
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| 303 | |
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| 304 | <pre><code>tuple<std::string, int, A> t1(std::string("same?"), 2, A()); |
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| 305 | tuple<std::string, long, A> t2(std::string("same?"), 2, A()); |
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| 306 | tuple<std::string, long, A> t3(std::string("different"), 3, A()); |
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| 307 | |
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| 308 | bool operator==(A, A) { std::cout << "All the same to me..."; return true; } |
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| 309 | |
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| 310 | t1 == t2; // true |
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| 311 | t1 == t3; // false, does not print "All the..." |
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| 312 | </code></pre> |
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| 313 | |
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| 314 | |
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| 315 | <h2><a name = "tiers">Tiers</a></h2> |
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| 316 | |
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| 317 | <p> |
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| 318 | <i>Tiers</i> are tuples, where all elements are of non-const reference types. |
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| 319 | They are constructed with a call to the <code>tie</code> function template (cf. <code>make_tuple</code>): |
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| 320 | |
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| 321 | <pre><code>int i; char c; double d; |
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| 322 | ... |
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| 323 | tie(i, c, a); |
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| 324 | </code></pre> |
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| 325 | |
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| 326 | <p> |
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| 327 | The above <code>tie</code> function creates a tuple of type <code>tuple<int&, char&, double&></code>. |
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| 328 | The same result could be achieved with the call <code>make_tuple(ref(i), ref(c), ref(a))</code>. |
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| 329 | </p> |
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| 330 | |
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| 331 | <p> |
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| 332 | A tuple that contains non-const references as elements can be used to 'unpack' another tuple into variables. E.g.: |
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| 333 | |
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| 334 | <pre><code>int i; char c; double d; |
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| 335 | tie(i, c, d) = make_tuple(1,'a', 5.5); |
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| 336 | std::cout << i << " " << c << " " << d; |
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| 337 | </code></pre> |
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| 338 | This code prints <code>1 a 5.5</code> to the standard output stream. |
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| 339 | |
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| 340 | A tuple unpacking operation like this is found for example in ML and Python. |
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| 341 | It is convenient when calling functions which return tuples. |
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| 342 | |
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| 343 | <p> |
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| 344 | The tying mechanism works with <code>std::pair</code> templates as well: |
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| 345 | |
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| 346 | <pre><code>int i; char c; |
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| 347 | tie(i, c) = std::make_pair(1, 'a'); |
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| 348 | </code></pre> |
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| 349 | <h4>Ignore</h4> |
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| 350 | There is also an object called <code>ignore</code> which allows you to ignore an element assigned by a tuple. |
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| 351 | The idea is that a function may return a tuple, only part of which you are interested in. For example (note, that <code>ignore</code> is under the <code>tuples</code> subnamespace): |
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| 352 | |
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| 353 | <pre><code>char c; |
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| 354 | tie(tuples::ignore, c) = std::make_pair(1, 'a'); |
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| 355 | </code></pre> |
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| 356 | |
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| 357 | <h2><a name = "streaming">Streaming</a></h2> |
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| 358 | |
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| 359 | <p> |
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| 360 | The global <code>operator<<</code> has been overloaded for <code>std::ostream</code> such that tuples are |
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| 361 | output by recursively calling <code>operator<<</code> for each element. |
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| 362 | </p> |
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| 363 | |
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| 364 | <p> |
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| 365 | Analogously, the global <code>operator>></code> has been overloaded to extract tuples from <code>std::istream</code> by recursively calling <code>operator>></code> for each element. |
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| 366 | </p> |
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| 367 | |
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| 368 | <p> |
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| 369 | The default delimiter between the elements is space, and the tuple is enclosed |
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| 370 | in parenthesis. |
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| 371 | For Example: |
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| 372 | |
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| 373 | <pre><code>tuple<float, int, std::string> a(1.0f, 2, std::string("Howdy folks!"); |
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| 374 | |
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| 375 | cout << a; |
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| 376 | </code></pre> |
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| 377 | outputs the tuple as: <code>(1.0 2 Howdy folks!)</code> |
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| 378 | |
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| 379 | <p> |
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| 380 | The library defines three <i>manipulators</i> for changing the default behavior: |
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| 381 | <ul> |
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| 382 | <li><code>set_open(char)</code> defines the character that is output before the first |
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| 383 | element.</li> |
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| 384 | <li><code>set_close(char)</code> defines the character that is output after the |
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| 385 | last element.</li> |
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| 386 | <li><code>set_delimiter(char)</code> defines the delimiter character between |
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| 387 | elements.</li> |
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| 388 | </ul> |
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| 389 | |
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| 390 | Note, that these manipulators are defined in the <code>tuples</code> subnamespace. |
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| 391 | For example: |
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| 392 | <code><pre>cout << tuples::set_open('[') << tuples::set_close(']') << tuples::set_delimiter(',') << a; |
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| 393 | </code></pre> |
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| 394 | outputs the same tuple <code>a</code> as: <code>[1.0,2,Howdy folks!]</code> |
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| 395 | |
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| 396 | <p>The same manipulators work with <code>operator>></code> and <code>istream</code> as well. Suppose the <code>cin</code> stream contains the following data: |
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| 397 | |
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| 398 | <pre><code>(1 2 3) [4:5]</code></pre> |
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| 399 | |
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| 400 | The code: |
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| 401 | |
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| 402 | <code><pre>tuple<int, int, int> i; |
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| 403 | tuple<int, int> j; |
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| 404 | |
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| 405 | cin >> i; |
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| 406 | cin >> tuples::set_open('[') >> tuples::set_close(']') >> tules::set_delimiter(':'); |
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| 407 | cin >> j; |
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| 408 | </code></pre> |
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| 409 | |
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| 410 | reads the data into the tuples <code>i</code> and <code>j</code>. |
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| 411 | |
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| 412 | <p> |
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| 413 | Note that extracting tuples with <code>std::string</code> or C-style string |
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| 414 | elements does not generally work, since the streamed tuple representation may not be unambiguously |
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| 415 | parseable. |
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| 416 | </p> |
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| 417 | |
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| 418 | <h2><a name = "performance">Performance</a></h2> |
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| 419 | |
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| 420 | All tuple access and construction functions are small inlined one-liners. |
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| 421 | Therefore, a decent compiler can eliminate any extra cost of using tuples compared to using hand written tuple like classes. |
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| 422 | Particularly, with a decent compiler there is no performance difference between this code: |
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| 423 | |
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| 424 | <pre><code>class hand_made_tuple { |
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| 425 | A a; B b; C c; |
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| 426 | public: |
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| 427 | hand_made_tuple(const A& aa, const B& bb, const C& cc) |
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| 428 | : a(aa), b(bb), c(cc) {}; |
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| 429 | A& getA() { return a; }; |
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| 430 | B& getB() { return b; }; |
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| 431 | C& getC() { return c; }; |
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| 432 | }; |
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| 433 | |
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| 434 | hand_made_tuple hmt(A(), B(), C()); |
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| 435 | hmt.getA(); hmt.getB(); hmt.getC(); |
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| 436 | </code></pre> |
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| 437 | |
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| 438 | and this code: |
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| 439 | |
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| 440 | <pre><code>tuple<A, B, C> t(A(), B(), C()); |
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| 441 | t.get<0>(); t.get<1>(); t.get<2>(); |
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| 442 | </code></pre> |
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| 443 | |
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| 444 | <p>Note, that there are widely used compilers (e.g. bcc 5.5.1) which fail to optimize this kind of tuple usage. |
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| 445 | </p> |
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| 446 | <p> |
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| 447 | Depending on the optimizing ability of the compiler, the tier mechanism may have a small performance penalty compared to using |
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| 448 | non-const reference parameters as a mechanism for returning multiple values from a function. |
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| 449 | For example, suppose that the following functions <code>f1</code> and <code>f2</code> have equivalent functionalities: |
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| 450 | |
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| 451 | <pre><code>void f1(int&, double&); |
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| 452 | tuple<int, double> f2(); |
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| 453 | </code></pre> |
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| 454 | |
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| 455 | Then, the call #1 may be slightly faster than #2 in the code below: |
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| 456 | |
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| 457 | <pre><code>int i; double d; |
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| 458 | ... |
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| 459 | f1(i,d); // #1 |
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| 460 | tie(i,d) = f2(); // #2 |
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| 461 | </code></pre> |
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| 462 | See |
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| 463 | [<a href="#publ_1">1</a>, |
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| 464 | <a href="#publ_2">2</a>] |
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| 465 | for more in-depth discussions about efficiency. |
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| 466 | |
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| 467 | <h4>Effect on Compile Time</h4> |
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| 468 | |
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| 469 | <p> |
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| 470 | Compiling tuples can be slow due to the excessive amount of template instantiations. |
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| 471 | Depending on the compiler and the tuple length, it may be more than 10 times slower to compile a tuple construct, compared to compiling an equivalent explicitly written class, such as the <code>hand_made_tuple</code> class above. |
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| 472 | However, as a realistic program is likely to contain a lot of code in addition to tuple definitions, the difference is probably unnoticeable. |
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| 473 | Compile time increases between 5 to 10 percentages were measured for programs which used tuples very frequently. |
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| 474 | With the same test programs, memory consumption of compiling increased between 22% to 27%. See |
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| 475 | [<a href="#publ_1">1</a>, |
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| 476 | <a href="#publ_2">2</a>] |
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| 477 | for details. |
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| 478 | </p> |
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| 479 | |
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| 480 | <h2><a name = "portability">Portability</a></h2> |
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| 481 | |
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| 482 | <p>The library code is(?) standard C++ and thus the library works with a standard conforming compiler. |
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| 483 | Below is a list of compilers and known problems with each compiler: |
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| 484 | </p> |
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| 485 | <table> |
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| 486 | <tr><td><u>Compiler</u></td><td><u>Problems</u></td></tr> |
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| 487 | <tr><td>gcc 2.95</td><td>-</td></tr> |
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| 488 | <tr><td>edg 2.44</td><td>-</td></tr> |
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| 489 | <tr><td>Borland 5.5</td><td>Can't use function pointers or member pointers as tuple elements</td></tr> |
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| 490 | <tr><td>Metrowerks 6.2</td><td>Can't use <code>ref</code> and <code>cref</code> wrappers</td></tr> |
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| 491 | <tr><td>MS Visual C++</td><td>No reference elements (<code>tie</code> still works). Can't use <code>ref</code> and <code>cref</code> wrappers</td></tr> |
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| 492 | </table> |
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| 493 | |
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| 494 | <h2><a name = "thanks">Acknowledgements</a></h2> |
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| 495 | Gary Powell has been an indispensable helping hand. In particular, stream manipulators for tuples were his idea. Doug Gregor came up with a working version for MSVC, David Abrahams found a way to get rid of most of the restrictions for compilers not supporting partial specialization. Thanks to Jeremy Siek, William Kempf and Jens Maurer for their help and suggestions. |
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| 496 | The comments by Vesa Karvonen, John Max Skaller, Ed Brey, Beman Dawes, David Abrahams and Hartmut Kaiser helped to improve the |
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| 497 | library. |
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| 498 | The idea for the tie mechanism came from an old usenet article by Ian McCulloch, where he proposed something similar for std::pairs. |
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| 499 | <h2><a name = "references">References</a></h2> |
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| 500 | |
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| 501 | <p> |
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| 502 | <a name="publ_1"></a>[1] |
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| 503 | Järvi J.: <i>Tuples and multiple return values in C++</i>, TUCS Technical Report No 249, 1999<!-- (<a href="http://www.tucs.fi/Publications">http://www.tucs.fi/Publications</a>)-->. |
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| 504 | </p> |
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| 505 | |
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| 506 | <p> |
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| 507 | <a name="publ_2"></a>[2] |
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| 508 | Järvi J.: <i>ML-Style Tuple Assignment in Standard C++ - Extending the Multiple Return Value Formalism</i>, TUCS Technical Report No 267, 1999<!-- (<a href="http://www.tucs.fi/Publications">http://www.tucs.fi/Publications</a>)-->. |
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| 509 | </p> |
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| 510 | |
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| 511 | <p> |
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| 512 | [3] Järvi J.:<i>Tuple Types and Multiple Return Values</i>, C/C++ Users Journal, August 2001. |
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| 513 | </p> |
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| 514 | |
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| 515 | <hr> |
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| 516 | |
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| 517 | <p>Last modified 2003-09-07</p> |
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| 518 | |
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| 519 | <p>© Copyright <a href="../../../people/jaakko_jarvi.htm"> Jaakko Järvi</a> 2001. |
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| 520 | |
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| 521 | Permission to copy, use, modify, sell and distribute this software and its documentation is granted provided this copyright notice appears in all copies. |
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| 522 | This software and its documentation is provided "as is" without express or implied warranty, and with no claim as to its suitability for any purpose. |
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| 523 | </p> |
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| 524 | </body> |
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| 525 | </html> |
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| 526 | |
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| 527 | |
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