epoc32/include/stdapis/boost/lambda/detail/ret.hpp
branchSymbian2
changeset 2 2fe1408b6811
     1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/epoc32/include/stdapis/boost/lambda/detail/ret.hpp	Tue Mar 16 16:12:26 2010 +0000
     1.3 @@ -0,0 +1,325 @@
     1.4 +// Boost Lambda Library  ret.hpp -----------------------------------------
     1.5 +
     1.6 +// Copyright (C) 1999, 2000 Jaakko Järvi (jaakko.jarvi@cs.utu.fi)
     1.7 +//
     1.8 +// Distributed under the Boost Software License, Version 1.0. (See
     1.9 +// accompanying file LICENSE_1_0.txt or copy at
    1.10 +// http://www.boost.org/LICENSE_1_0.txt)
    1.11 +//
    1.12 +// For more information, see www.boost.org
    1.13 +
    1.14 +
    1.15 +#ifndef BOOST_LAMBDA_RET_HPP
    1.16 +#define BOOST_LAMBDA_RET_HPP
    1.17 +
    1.18 +namespace boost { 
    1.19 +namespace lambda {
    1.20 +
    1.21 +  // TODO:
    1.22 +
    1.23 +//  Add specializations for function references for ret, protect and unlambda
    1.24 +//  e.g void foo(); unlambda(foo); fails, as it would add a const qualifier
    1.25 +  // for a function type. 
    1.26 +  // on the other hand unlambda(*foo) does work
    1.27 +
    1.28 +
    1.29 +// -- ret -------------------------
    1.30 +// the explicit return type template 
    1.31 +
    1.32 +  // TODO: It'd be nice to make ret a nop for other than lambda functors
    1.33 +  // but causes an ambiguiyty with gcc (not with KCC), check what is the
    1.34 +  // right interpretation.
    1.35 +
    1.36 +  //  // ret for others than lambda functors has no effect
    1.37 +  // template <class U, class T>
    1.38 +  // inline const T& ret(const T& t) { return t; }
    1.39 +
    1.40 +
    1.41 +template<class RET, class Arg>
    1.42 +inline const 
    1.43 +lambda_functor<
    1.44 +  lambda_functor_base<
    1.45 +    explicit_return_type_action<RET>, 
    1.46 +    tuple<lambda_functor<Arg> >
    1.47 +  > 
    1.48 +>
    1.49 +ret(const lambda_functor<Arg>& a1)
    1.50 +{
    1.51 +  return  
    1.52 +    lambda_functor_base<
    1.53 +      explicit_return_type_action<RET>, 
    1.54 +      tuple<lambda_functor<Arg> >
    1.55 +    > 
    1.56 +    (tuple<lambda_functor<Arg> >(a1));
    1.57 +}
    1.58 +
    1.59 +// protect ------------------
    1.60 +
    1.61 +  // protecting others than lambda functors has no effect
    1.62 +template <class T>
    1.63 +inline const T& protect(const T& t) { return t; }
    1.64 +
    1.65 +template<class Arg>
    1.66 +inline const 
    1.67 +lambda_functor<
    1.68 +  lambda_functor_base<
    1.69 +    protect_action, 
    1.70 +    tuple<lambda_functor<Arg> >
    1.71 +  > 
    1.72 +>
    1.73 +protect(const lambda_functor<Arg>& a1)
    1.74 +{
    1.75 +  return 
    1.76 +      lambda_functor_base<
    1.77 +        protect_action, 
    1.78 +        tuple<lambda_functor<Arg> >
    1.79 +      > 
    1.80 +    (tuple<lambda_functor<Arg> >(a1));
    1.81 +}
    1.82 +   
    1.83 +// -------------------------------------------------------------------
    1.84 +
    1.85 +// Hides the lambda functorness of a lambda functor. 
    1.86 +// After this, the functor is immune to argument substitution, etc.
    1.87 +// This can be used, e.g. to make it safe to pass lambda functors as 
    1.88 +// arguments to functions, which might use them as target functions
    1.89 +
    1.90 +// note, unlambda and protect are different things. Protect hides the lambda
    1.91 +// functor for one application, unlambda for good.
    1.92 +
    1.93 +template <class LambdaFunctor>
    1.94 +class non_lambda_functor
    1.95 +{
    1.96 +  LambdaFunctor lf;
    1.97 +public:
    1.98 +  
    1.99 +  // This functor defines the result_type typedef.
   1.100 +  // The result type must be deducible without knowing the arguments
   1.101 +
   1.102 +  template <class SigArgs> struct sig {
   1.103 +    typedef typename 
   1.104 +      LambdaFunctor::inherited:: 
   1.105 +        template sig<typename SigArgs::tail_type>::type type;
   1.106 +  };
   1.107 +
   1.108 +  explicit non_lambda_functor(const LambdaFunctor& a) : lf(a) {}
   1.109 +
   1.110 +  typename LambdaFunctor::nullary_return_type  
   1.111 +  operator()() const {
   1.112 +    return lf.template 
   1.113 +      call<typename LambdaFunctor::nullary_return_type>
   1.114 +        (cnull_type(), cnull_type(), cnull_type(), cnull_type()); 
   1.115 +  }
   1.116 +
   1.117 +  template<class A>
   1.118 +  typename sig<tuple<const non_lambda_functor, A&> >::type 
   1.119 +  operator()(A& a) const {
   1.120 +    return lf.template call<typename sig<tuple<const non_lambda_functor, A&> >::type >(a, cnull_type(), cnull_type(), cnull_type()); 
   1.121 +  }
   1.122 +
   1.123 +  template<class A, class B>
   1.124 +  typename sig<tuple<const non_lambda_functor, A&, B&> >::type 
   1.125 +  operator()(A& a, B& b) const {
   1.126 +    return lf.template call<typename sig<tuple<const non_lambda_functor, A&, B&> >::type >(a, b, cnull_type(), cnull_type()); 
   1.127 +  }
   1.128 +
   1.129 +  template<class A, class B, class C>
   1.130 +  typename sig<tuple<const non_lambda_functor, A&, B&, C&> >::type 
   1.131 +  operator()(A& a, B& b, C& c) const {
   1.132 +    return lf.template call<typename sig<tuple<const non_lambda_functor, A&, B&, C&> >::type>(a, b, c, cnull_type()); 
   1.133 +  }
   1.134 +};
   1.135 +
   1.136 +template <class Arg>
   1.137 +inline const Arg& unlambda(const Arg& a) { return a; }
   1.138 +
   1.139 +template <class Arg>
   1.140 +inline const non_lambda_functor<lambda_functor<Arg> > 
   1.141 +unlambda(const lambda_functor<Arg>& a)
   1.142 +{
   1.143 +  return non_lambda_functor<lambda_functor<Arg> >(a);
   1.144 +}
   1.145 +
   1.146 +  // Due to a language restriction, lambda functors cannot be made to
   1.147 +  // accept non-const rvalue arguments. Usually iterators do not return 
   1.148 +  // temporaries, but sometimes they do. That's why a workaround is provided.
   1.149 +  // Note, that this potentially breaks const correctness, so be careful!
   1.150 +
   1.151 +// any lambda functor can be turned into a const_incorrect_lambda_functor
   1.152 +// The operator() takes arguments as consts and then casts constness
   1.153 +// away. So this breaks const correctness!!! but is a necessary workaround
   1.154 +// in some cases due to language limitations.
   1.155 +// Note, that this is not a lambda_functor anymore, so it can not be used
   1.156 +// as a sub lambda expression.
   1.157 +
   1.158 +template <class LambdaFunctor>
   1.159 +struct const_incorrect_lambda_functor {
   1.160 +  LambdaFunctor lf;
   1.161 +public:
   1.162 +
   1.163 +  explicit const_incorrect_lambda_functor(const LambdaFunctor& a) : lf(a) {}
   1.164 +
   1.165 +  template <class SigArgs> struct sig {
   1.166 +    typedef typename
   1.167 +      LambdaFunctor::inherited::template 
   1.168 +        sig<typename SigArgs::tail_type>::type type;
   1.169 +  };
   1.170 +
   1.171 +  // The nullary case is not needed (no arguments, no parameter type problems)
   1.172 +
   1.173 +  template<class A>
   1.174 +  typename sig<tuple<const const_incorrect_lambda_functor, A&> >::type
   1.175 +  operator()(const A& a) const {
   1.176 +    return lf.template call<typename sig<tuple<const const_incorrect_lambda_functor, A&> >::type >(const_cast<A&>(a), cnull_type(), cnull_type(), cnull_type());
   1.177 +  }
   1.178 +
   1.179 +  template<class A, class B>
   1.180 +  typename sig<tuple<const const_incorrect_lambda_functor, A&, B&> >::type
   1.181 +  operator()(const A& a, const B& b) const {
   1.182 +    return lf.template call<typename sig<tuple<const const_incorrect_lambda_functor, A&, B&> >::type >(const_cast<A&>(a), const_cast<B&>(b), cnull_type(), cnull_type());
   1.183 +  }
   1.184 +
   1.185 +  template<class A, class B, class C>
   1.186 +  typename sig<tuple<const const_incorrect_lambda_functor, A&, B&, C&> >::type
   1.187 +  operator()(const A& a, const B& b, const C& c) const {
   1.188 +    return lf.template call<typename sig<tuple<const const_incorrect_lambda_functor, A&, B&, C&> >::type>(const_cast<A&>(a), const_cast<B&>(b), const_cast<C&>(c), cnull_type());
   1.189 +  }
   1.190 +};
   1.191 +
   1.192 +// ------------------------------------------------------------------------
   1.193 +// any lambda functor can be turned into a const_parameter_lambda_functor
   1.194 +// The operator() takes arguments as const.
   1.195 +// This is useful if lambda functors are called with non-const rvalues.
   1.196 +// Note, that this is not a lambda_functor anymore, so it can not be used
   1.197 +// as a sub lambda expression.
   1.198 +
   1.199 +template <class LambdaFunctor>
   1.200 +struct const_parameter_lambda_functor {
   1.201 +  LambdaFunctor lf;
   1.202 +public:
   1.203 +
   1.204 +  explicit const_parameter_lambda_functor(const LambdaFunctor& a) : lf(a) {}
   1.205 +
   1.206 +  template <class SigArgs> struct sig {
   1.207 +    typedef typename
   1.208 +      LambdaFunctor::inherited::template 
   1.209 +        sig<typename SigArgs::tail_type>::type type;
   1.210 +  };
   1.211 +
   1.212 +  // The nullary case is not needed: no arguments, no constness problems.
   1.213 +
   1.214 +  template<class A>
   1.215 +  typename sig<tuple<const const_parameter_lambda_functor, const A&> >::type
   1.216 +  operator()(const A& a) const {
   1.217 +    return lf.template call<typename sig<tuple<const const_parameter_lambda_functor, const A&> >::type >(a, cnull_type(), cnull_type(), cnull_type());
   1.218 +  }
   1.219 +
   1.220 +  template<class A, class B>
   1.221 +  typename sig<tuple<const const_parameter_lambda_functor, const A&, const B&> >::type
   1.222 +  operator()(const A& a, const B& b) const {
   1.223 +    return lf.template call<typename sig<tuple<const const_parameter_lambda_functor, const A&, const B&> >::type >(a, b, cnull_type(), cnull_type());
   1.224 +  }
   1.225 +
   1.226 +  template<class A, class B, class C>
   1.227 +  typename sig<tuple<const const_parameter_lambda_functor, const A&, const B&, const C&>
   1.228 +>::type
   1.229 +  operator()(const A& a, const B& b, const C& c) const {
   1.230 +    return lf.template call<typename sig<tuple<const const_parameter_lambda_functor, const A&, const B&, const C&> >::type>(a, b, c, cnull_type());
   1.231 +  }
   1.232 +};
   1.233 +
   1.234 +template <class Arg>
   1.235 +inline const const_incorrect_lambda_functor<lambda_functor<Arg> >
   1.236 +break_const(const lambda_functor<Arg>& lf)
   1.237 +{
   1.238 +  return const_incorrect_lambda_functor<lambda_functor<Arg> >(lf);
   1.239 +}
   1.240 +
   1.241 +
   1.242 +template <class Arg>
   1.243 +inline const const_parameter_lambda_functor<lambda_functor<Arg> >
   1.244 +const_parameters(const lambda_functor<Arg>& lf)
   1.245 +{
   1.246 +  return const_parameter_lambda_functor<lambda_functor<Arg> >(lf);
   1.247 +}
   1.248 +
   1.249 +// make void ------------------------------------------------
   1.250 +// make_void( x ) turns a lambda functor x with some return type y into
   1.251 +// another lambda functor, which has a void return type
   1.252 +// when called, the original return type is discarded
   1.253 +
   1.254 +// we use this action. The action class will be called, which means that
   1.255 +// the wrapped lambda functor is evaluated, but we just don't do anything
   1.256 +// with the result.
   1.257 +struct voidifier_action {
   1.258 +  template<class Ret, class A> static void apply(A&) {}
   1.259 +};
   1.260 +
   1.261 +template<class Args> struct return_type_N<voidifier_action, Args> {
   1.262 +  typedef void type;
   1.263 +};
   1.264 +
   1.265 +template<class Arg1>
   1.266 +inline const 
   1.267 +lambda_functor<
   1.268 +  lambda_functor_base<
   1.269 +    action<1, voidifier_action>,
   1.270 +    tuple<lambda_functor<Arg1> >
   1.271 +  > 
   1.272 +> 
   1.273 +make_void(const lambda_functor<Arg1>& a1) { 
   1.274 +return 
   1.275 +    lambda_functor_base<
   1.276 +      action<1, voidifier_action>,
   1.277 +      tuple<lambda_functor<Arg1> >
   1.278 +    > 
   1.279 +  (tuple<lambda_functor<Arg1> > (a1));
   1.280 +}
   1.281 +
   1.282 +// for non-lambda functors, make_void does nothing 
   1.283 +// (the argument gets evaluated immediately)
   1.284 +
   1.285 +template<class Arg1>
   1.286 +inline const 
   1.287 +lambda_functor<
   1.288 +  lambda_functor_base<do_nothing_action, null_type> 
   1.289 +> 
   1.290 +make_void(const Arg1& a1) { 
   1.291 +return 
   1.292 +    lambda_functor_base<do_nothing_action, null_type>();
   1.293 +}
   1.294 +
   1.295 +// std_functor -----------------------------------------------------
   1.296 +
   1.297 +//  The STL uses the result_type typedef as the convention to let binders know
   1.298 +//  the return type of a function object. 
   1.299 +//  LL uses the sig template.
   1.300 +//  To let LL know that the function object has the result_type typedef 
   1.301 +//  defined, it can be wrapped with the std_functor function.
   1.302 +
   1.303 +
   1.304 +// Just inherit form the template parameter (the standard functor), 
   1.305 +// and provide a sig template. So we have a class which is still the
   1.306 +// same functor + the sig template.
   1.307 +
   1.308 +template<class T>
   1.309 +struct result_type_to_sig : public T {
   1.310 +  template<class Args> struct sig { typedef typename T::result_type type; };
   1.311 +  result_type_to_sig(const T& t) : T(t) {}
   1.312 +};
   1.313 +
   1.314 +template<class F>
   1.315 +inline result_type_to_sig<F> std_functor(const F& f) { return f; }
   1.316 +
   1.317 +
   1.318 +} // namespace lambda 
   1.319 +} // namespace boost
   1.320 +
   1.321 +#endif
   1.322 +
   1.323 +
   1.324 +
   1.325 +
   1.326 +
   1.327 +
   1.328 +