NAME

       FBB::PtrIter - Iterator returning pointer when dereferenced

SYNOPSIS

       #include <bobcat/ptriter>

DESCRIPTION

       The  PtrIter  class  template  implements  an  input  iterator whose operator* returns the
       address of the element the iterator refers to.  Consider a std::unordered_map<std::string,
       DataType>.   Its   begin   member   returns   an   iterator   whose  operator*  returns  a
       std::pair<std::string, DataType> (const) &. This is usually what you want, but now  assume
       we  want to display the map’s content, sorted by its keys. Sorting can simply be performed
       by defining a support vector containing pointers to the elements  in  the  map,  and  then
       sorting the strings the pointers point at.

       PtrIter  is  a  tool  that can be used to construct such a support vector, as shown in the
       EXAMPLE section.

       PtrIter is  a  class  template  requiring  one  template  type  parameter:  Iterator,  the
       iterator’s type (e.g., vector<string>::iterator)

       PtrIter’s  users  don’t  have  to  specify  PtrIter’s template type. The function template
       ptrIter, when provided with an iterator returns the matching PtrIter object.

NAMESPACE

       FBB
       All constructors, members, operators and manipulators, mentioned  in  this  man-page,  are
       defined in the namespace FBB.

INHERITS FROM

       std::iterator<std::input_iterator_tag, ...>

FREE FUNCTION

       o      PtrIter<Iterator> ptrIter(Iterator const &iter):
              this  function  template  returns  a  PtrIter  object  for  the function’s Iterator
              argument. This function template simplyfies the construction of  a  PtrIter  as  no
              template parameters need to be specified (see also the EXAMPLE section)

CONSTRUCTORS

       o      PtrIter(Iterator const &iter):
              The  iter  parameter  must be initialized with an existing input iterator, offering
              operator*, operator++, operator== and operator!=.  As PtrIter is a class  template,
              its  template  type  parameters  must  be specified when defining a PtrIter object.
              E.g.,

                  PtrIter<set<string>::iterator> PtrIter(mySet.begin());

       Copy and move constructors (and assignment operators) are available.

OVERLOADED OPERATORS

       o      PtrType operator*() const:
              the address of the entity the iterator refers to is returned;

       o      PtrIter &operator++():
              the iterator is (pre)incremented to the next position;

       o      bool operator==(PtrIter const &other) const:
              true is returned if the two iterators are equal;

       o      bool operator!=(PtrIter const &other) const:
              true is returned if the two iterators are unequal;

USING DECLARATION

       The PtrIter class template defines PtrType:

       o      using PtrType = decltype(&*Iterator()):

MEMBER FUNCTIONS

       All members of std::iterator<std:::input_iterator_tag, ...> are available, as FBB::PtrIter
       inherits from this class.

EXAMPLE

       #include <algorithm>
       #include <unordered_map>
       #include <vector>
       #include <cstring>
       #include <iostream>

       #include <bobcat/ptriter>

       using namespace std;
       using namespace FBB;

       int main()
       {
           cout << "Enter lines, the first word will be the map’s key; "
                                                   "^D when done.\n";

           string key;
           string line;
           unordered_map<string, string> map;
           while (cin >> key && getline(cin, line))    // fill the map
               map[key] = line;
           cout << ’\n’;

                                               // initialize a support
           vector<decltype(&*map.begin())>     // vector, using ptrIter
               support(ptrIter(map.begin()), ptrIter(map.end()));

                                               // sort ’support’
           typedef unordered_map<string, string>::value_type VT;
           sort(support.begin(), support.end(),
               [&](VT const *p1, VT const *p2)
               {
                   return strcasecmp(p1->first.c_str(), p2->first.c_str()) < 0;
               }
           );

           for(auto &element: support)         // display sorted by key
               cout << element->first << ’ ’ << element->second << ’\n’;
       }

FILES

       bobcat/ptriter - defines the class interface

SEE ALSO

       bobcat(7)

BUGS

       None Reported.

BOBCAT PROJECT FILES

       o      https://fbb-git.gitlab.io/bobcat/: gitlab project page;

       o      bobcat_6.04.00-x.dsc: detached signature;

       o      bobcat_6.04.00-x.tar.gz: source archive;

       o      bobcat_6.04.00-x_i386.changes: change log;

       o      libbobcat1_6.04.00-x_*.deb: debian package containing the libraries;

       o      libbobcat1-dev_6.04.00-x_*.deb:  debian  package  containing the libraries, headers
              and manual pages;

BOBCAT

       Bobcat is an acronym of `Brokken’s Own Base Classes And Templates’.

COPYRIGHT

       This is free software, distributed under the terms  of  the  GNU  General  Public  License
       (GPL).

AUTHOR

       Frank B. Brokken (f.b.brokken@rug.nl).