.TH "FBB::PtrIter" "3bobcat" "2005\-2020" "libbobcat\-dev_5\&.07\&.00" "Error handler"

.PP 
.SH "NAME"
FBB::PtrIter \- Iterator returning pointer when dereferenced 
.PP 
.SH "SYNOPSIS"
\fB#include <bobcat/ptriter>\fP
.br 

.PP 
.SH "DESCRIPTION"

.PP 
The \fIPtrIter\fP class template implements an input iterator whose
\fIoperator*\fP returns the address of the element the iterator refers to\&.
Consider a \fIstd::unordered_map<std::string, DataType>\fP\&. Its \fIbegin\fP member
returns an iterator whose \fIoperator*\fP returns a \fIstd::pair<std::string,
DataType> (const) &\fP\&. This is usually what you want, but now assume we want to
display the map\(cq\&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\&.
.PP 
\fIPtrIter\fP is a tool that can be used to construct such a support vector, as
shown in the \fBEXAMPLE\fP section\&.
.PP 
\fIPtrIter\fP is a class template requiring one template type parameter:
\fIIterator\fP, the iterator\(cq\&s type (e\&.g\&., \fIvector<string>::iterator\fP)
.PP 
\fIPtrIter\fP\(cq\&s users don\(cq\&t have to specify \fIPtrIter\fP\(cq\&s template type\&. The
function template \fIptrIter\fP, when provided with an iterator returns the
matching \fIPtrIter\fP object\&.
.PP 
.SH "NAMESPACE"
\fBFBB\fP
.br 
All constructors, members, operators and manipulators, mentioned in this
man\-page, are defined in the namespace \fBFBB\fP\&.
.PP 
.SH "INHERITS FROM"
\fIstd::iterator<std::input_iterator_tag, \&.\&.\&.>\fP
.PP 
.SH "FREE FUNCTION"
.IP o 
\fBPtrIter<Iterator> ptrIter(Iterator const &iter)\fP:
.br 
this function template returns a \fIPtrIter\fP object for the function\(cq\&s
\fIIterator\fP argument\&. This function template simplyfies the construction of a
\fIPtrIter\fP as no template parameters need to be specified (see also the
\fBEXAMPLE\fP section)

.PP 
.SH "CONSTRUCTORS"
.IP o 
\fBPtrIter(Iterator const &iter)\fP:
.br 
The \fIiter\fP parameter must be initialized with an existing input
iterator, offering \fIoperator*, operator++, operator==\fP and \fIoperator!=\fP\&.
As \fIPtrIter\fP is a class template, its template type parameters must be
specified when defining a \fIPtrIter\fP object\&. E\&.g\&.,
.nf 

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

.PP 
Copy and move constructors (and assignment operators) are available\&.
.PP 
.SH "OVERLOADED OPERATORS"
.IP o 
\fBPtrType operator*() const\fP:
.br 
the address of the entity the iterator refers to is returned;
.IP o 
\fBPtrIter &operator++()\fP:
.br 
the iterator is (pre)incremented to the next position;
.IP o 
\fBbool operator==(PtrIter const &other) const\fP:
.br 
\fItrue\fP is returned if the two iterators are equal;
.IP o 
\fBbool operator!=(PtrIter const &other) const\fP:
.br 
\fItrue\fP is returned if the two iterators are unequal;

.PP 
.SH "DEFINED TYPE"
\fIPtrIter\fP defines the following type:
.IP o 
\fBtypedef decltype(&*Iterator()) PtrType\fP:
.br 

.PP 
.SH "MEMBER FUNCTIONS"
All members of \fIstd::iterator<std:::input_iterator_tag, \&.\&.\&.>\fP are
available, as \fBFBB::PtrIter\fP inherits from this class\&.
.PP 
.SH "EXAMPLE"
.nf 
#include <algorithm>
#include <unordered_map>
#include <vector>
#include <cstring>
#include <iostream>

#include <bobcat/ptriter>

using namespace std;
using namespace FBB;

int main()
{
    cout << \(dq\&Enter lines, the first word will be the map\(cq\&s key; \(dq\&
                                            \(dq\&^D when done\&.\en\(dq\&;

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

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

                                        // sort \(cq\&support\(cq\&
    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 << \(cq\& \(cq\& << element\->second << \(cq\&\en\(cq\&;
}







.fi 

.PP 
.SH "FILES"
\fIbobcat/ptriter\fP \- defines the class interface
.PP 
.SH "SEE ALSO"
\fBbobcat\fP(7)
.PP 
.SH "BUGS"
None Reported\&.
.PP 
.SH "BOBCAT PROJECT FILES"

.PP 
.IP o 
\fIhttps://fbb\-git\&.gitlab\&.io/bobcat/\fP: gitlab project page;
.IP o 
\fIbobcat_5\&.07\&.00\-x\&.dsc\fP: detached signature;
.IP o 
\fIbobcat_5\&.07\&.00\-x\&.tar\&.gz\fP: source archive;
.IP o 
\fIbobcat_5\&.07\&.00\-x_i386\&.changes\fP: change log;
.IP o 
\fIlibbobcat1_5\&.07\&.00\-x_*\&.deb\fP: debian package containing the
libraries;
.IP o 
\fIlibbobcat1\-dev_5\&.07\&.00\-x_*\&.deb\fP: debian package containing the
libraries, headers and manual pages;

.PP 
.SH "BOBCAT"
Bobcat is an acronym of `Brokken\(cq\&s Own Base Classes And Templates\(cq\&\&.
.PP 
.SH "COPYRIGHT"
This is free software, distributed under the terms of the 
GNU General Public License (GPL)\&.
.PP 
.SH "AUTHOR"
Frank B\&. Brokken (\fBf\&.b\&.brokken@rug\&.nl\fP)\&.
.PP