Dune::ForLoop< Operation, first, last > Class Template Reference

A static loop using TMP. More...

#include <dune/common/forloop.hh>

Detailed Description

template<template< int > class Operation, int first, int last>
class Dune::ForLoop< Operation, first, last >

A static loop using TMP.

The ForLoop takes a

template<int i> class Operation 

template argument with a static apply method which is called for i=first...last (first<=last are int template arguments). A specialization for class template class Operation for i=first or i=last is not required. The class Operation must provide a static void function apply(...). Arguments (as references) can be passed through the ForLoop to this function (up to 5 at the moment).

It is possible to pass a subclass to the ForLoop (since no specialization is needed).

Example of usage:

template<class Tuple>
struct PrintTupleTypes
{
  template <int i>
  struct Operation
  {
    template<class Stream>
    static void apply(Stream &stream, const std::string &prefix)
    {
      stream << prefix << i << ": "
             << className<typename tuple_element<i, Tuple>::type>()
             << std::endl;
    }
  };
  template<class Stream>
  static void print(Stream &stream, const std::string &prefix)
  {
    // cannot attach on-the-fly in the argument to ForLoop<..>::apply() since
    // that would yield an rvalue
    std::string extended_prefix = prefix+"  ";
 
    stream << prefix << "tuple<" << std::endl;
    ForLoop<Operation, 0, tuple_size<Tuple>::value-1>::
      apply(stream, extended_prefix);
    stream << prefix << ">" << std::endl;
  }
};

Note

Don't use any rvalues as the arguments to apply().

Rvalues will bind to const-references, but not to references that are non-const. Since we do want to support modifiable arguments to apply(), we have to use non-const references as arguments. Supporting const references as well would lead to an insane number of overloads which all have to be written more-or-less by hand.

Examples of rvalues are: literals (1.0, 0, "huhu"), the results of functions returning an object (std::make_pair(0, 1.0)) and temporary object constructions (std::string("hello"));

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The documentation for this class was generated from the following file:

• dune/common/forloop.hh