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1 // Copyright Daniel Wallin, David Abrahams 2005. Use, modification and |
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2 // distribution is subject to the Boost Software License, Version 1.0. (See |
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3 // accompanying file LICENSE_1_0.txt or copy at |
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4 // http://www.boost.org/LICENSE_1_0.txt) |
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5 |
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6 #ifndef DEFAULT_050329_HPP |
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7 #define DEFAULT_050329_HPP |
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8 |
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9 namespace boost { namespace parameter { namespace aux { |
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10 |
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11 // A wrapper for the default value passed by the user when resolving |
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12 // the value of the parameter with the given Keyword |
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13 template <class Keyword, class Value> |
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14 struct default_ |
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15 { |
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16 default_(Value& x) |
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17 : value(x) |
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18 {} |
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19 |
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20 Value& value; |
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21 }; |
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22 |
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23 // |
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24 // lazy_default -- |
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25 // |
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26 // A wrapper for the default value computation function passed by |
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27 // the user when resolving the value of the parameter with the |
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28 // given keyword |
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29 // |
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30 #if BOOST_WORKAROUND(__EDG_VERSION__, <= 300) |
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31 // These compilers need a little extra help with overload |
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32 // resolution; we have empty_arg_list's operator[] accept a base |
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33 // class to make that overload less preferable. |
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34 template <class KW, class DefaultComputer> |
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35 struct lazy_default_base |
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36 { |
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37 lazy_default_base(DefaultComputer const& x) |
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38 : compute_default(x) |
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39 {} |
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40 DefaultComputer const& compute_default; |
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41 }; |
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42 |
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43 template <class KW, class DefaultComputer> |
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44 struct lazy_default |
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45 : lazy_default_base<KW,DefaultComputer> |
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46 { |
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47 lazy_default(DefaultComputer const & x) |
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48 : lazy_default_base<KW,DefaultComputer>(x) |
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49 {} |
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50 }; |
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51 # define BOOST_PARAMETER_lazy_default_fallback lazy_default_base |
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52 #else |
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53 template <class KW, class DefaultComputer> |
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54 struct lazy_default |
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55 { |
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56 lazy_default(const DefaultComputer& x) |
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57 : compute_default(x) |
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58 {} |
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59 DefaultComputer const& compute_default; |
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60 }; |
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61 # define BOOST_PARAMETER_lazy_default_fallback lazy_default |
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62 #endif |
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63 |
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64 }}} // namespace boost::parameter::aux |
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65 |
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66 #endif // DEFAULT_050329_HPP |
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67 |