lexer.h
<code C++>
#ifndef LEXER_H
#define LEXER_H

#include <string>
#include <fstream>
using namespace std;

enum TokenKind { ident, number, text, separator, eos };

class Lexer
{
private:
   ifstream f;
   char ch;
   void nextChar ();

public:
   TokenKind kind;
   string token;
   void nextToken ();
   void error (string msg);

   bool isSeparator (char c);
   void checkSeparator (char c);
   string readIdent ();


public:
    Lexer (string fileName);
};

#endif // LEXER_H
</code>

lexer.cpp
<code C++>
#include "lexer.h"
#include <iostream> // cout

const char zero = 0;

Lexer::Lexer (string fileName)
{
   f.open (fileName);
   if (! f.good ())
       error ("Cannot open file: " + fileName);

   ch = zero;
   nextChar ();
   nextToken ();
}

void Lexer::error (string msg)
{
    cout << "Error: " << msg << endl;
    exit (1);
}

void Lexer::nextChar()
{
    f >> ch;
    if (! f.good ())
       ch = zero;
}

void Lexer::nextToken()
{
    token = "";
    while (ch != zero && ch <= ' ')
        nextChar ();

    if (ch >= 'a' && ch <= 'z' || ch >= 'A' && ch <= 'Z')
    {
        kind = ident;
        while (ch >= 'a' && ch <= 'z' || ch >= 'A' && ch <= 'Z')
        {
            token = token + ch;
            nextChar ();
        }
    }
    else if (ch >= '0' && ch <= '9')
    {
        kind = number;
        while (ch >= '0' && ch <= '9')
        {
            token = token + ch;
            nextChar ();
        }
    }
    else if (ch != zero)
    {
        kind = separator;
        token = string (1, ch);
        nextChar ();
    }
    else
    {
        kind = eos;
    }
}

bool Lexer::isSeparator (char c)
{
    return kind==separator && token==string(1, c);
}

void Lexer::checkSeparator(char c)
{
    if (!isSeparator(c)) error(string (1,c)+" expected");
    nextToken();
}

string Lexer:: readIdent ()
{
    if (kind!=ident)
        error("Identifire expected.");
    string result = token;
    nextToken();
    return result;
}
</code>

list.h
<code C++>
#ifndef LIST_H
#define LIST_H

#include <string>

using namespace std;

class Item;

// double sqr (double x) { return x*x; }

class List
{  
private:
    Item * first;
    Item * last;

public:
    Item * getFirst () { return first; }
    Item * getLast () { return last; }

public:
    List (); // konstruktor
    ~ List (); // destruktor

    void insertFirst (string name0);
    void insertLast (string name0);

    void linkFirst (Item * p);
    void linkLast (Item * p);

    void linkBefore (Item * old, Item * p); // vloz p pred old
    void linkAfter (Item * old, Item * p); // vloz p za old

    void unlink (Item * p); // odpoj p ze seznamu

    void print ();
    void insert (string name0);
    void move (List & target); // presunout vsechny prvky z this do target
    void transfer (List & source); // presunout vsechny prvky ze source do this
    void reverse ();

private:
    void link (Item * a, Item * b, Item * c); // pripoj b v poradi a, b, c
    // b novy, zatim neni v senamu
    // a predchudce, muze byt nulovy
    // c naslednik, muze byt nulovy
};

class Item
{
private:
    string name;
    List * owner;
    Item * prev;
    Item * next;
public:
    string getName () { return name; }
    Item * getPrev () { return prev; }
    Item * getNext () { return next; }
public:
    Item (string name0 = "");
    friend class List;
};

#endif // LIST_H
</code>

list.cpp
<code C++>
#include "list.h"

// #include <assert.h>
#include <cassert>

#include <iostream>

using namespace std;

List::List() :
    first (nullptr),
    last (nullptr)
{
}

Item::Item (string name0) :
    name (name0),
    owner (nullptr),
    prev (nullptr),
    next (nullptr)
{
}

void List::insertFirst (string name0)
{
    linkFirst ( new Item (name0) );
}

void List::insertLast (string name0)
{
    // Item * p = new Item;
    // p->name = name0;
    Item * p = new Item (name0);
    linkLast (p);
}

void List::linkFirst(Item *p)
{
    link (nullptr, p, first);
}

void List::linkLast(Item *p)
{
    link (last, p, nullptr);
}

void List::linkBefore (Item *old, Item *p)
// vloz p pred old
{
    assert (old != nullptr);
    link (old->prev, p, old);
}

void List::linkAfter(Item *old, Item *p)
// vloz p za old
{
    assert (old != nullptr);
    link (old, p, old->next);
}

void List::link(Item *a, Item *b, Item *c)
{
    // #include <cassert>
    assert (b != nullptr);

    assert (b->owner == nullptr);
    b->owner = this;

    assert (a == nullptr || a->owner == this);
    assert (c == nullptr || c->owner == this);

    b->prev = a;
    b->next = c;

    if (a != nullptr)
       a->next = b;
    else
       first = b;

    if (c != nullptr)
       c->prev = b;
    else
       last = b;
}

void List::unlink (Item *p)
{
    assert (p != nullptr);
    assert (p->owner == this);

    Item * a = p->prev;
    Item * c = p->next;

    if (a != nullptr)
       a->next = c; // mame predchudce, muzeme propojit
    else
       first = c; // nemame predchudce, naslednik se stava prvnim

    if (c != nullptr)
       c->prev = a;
    else
       last = a;

    p->owner = nullptr;
    p->prev = nullptr;
    p->next = nullptr;
}

List::~List()
{
   Item * p = first;
   while (p != nullptr)
   {
       Item * t = p->next;
       unlink (p);
       // cout << "Mazeme " << p->name << endl;
       delete p;
       p = t;
   }
}

void List::move (List & target)
{
    Item * p = first;
    while (p != nullptr)
    {
        Item * t = p->next;
        unlink (p);
        target.linkLast (p);
        p = t;
    }
}

void List::transfer (List & source)
{
    Item * p = source.first;
    while (p != nullptr)
    {
        Item * t = p->next;
        source.unlink (p);
        linkLast (p);
        p = t;
    }
}

void List::reverse ()
{
    List target;

    Item * p = first;
    while (p != nullptr)
    {
        Item * t = p->next;
        unlink (p);
        target.linkFirst (p);
        p = t;
    }

    target.move (*this);
}

void List::print ()
{
   // #include <iostream>
   cout << "[" << endl;

   Item * p = first;
   while (p != nullptr)
   {
       cout << p->name << endl;
       p = p->next;
   }

   cout << "]" << endl << endl;
}

void List::insert (string name0)
{
    Item * t = first;
    while (t != nullptr && t->name <= name0)
        t = t->next;

    Item * p = new Item (name0);
    if (t != nullptr)
        linkBefore (t, p);
    else
        linkLast (p);
}
</code>

main.cpp
<code C++>
#include <iostream>
#include "lexer.h"
#include "list.h"

using namespace std;

int main()
{
    List a;
    Lexer f ("../lexer/abc.txt");

    f.checkSeparator('{');
    if (! f.isSeparator('}'))
    {
        a.insertLast (f.readIdent ());
        while (f.isSeparator (','))
        {
           f.nextToken ();
           a.insertLast (f.readIdent ());
        }
    }
    f.checkSeparator('}');

    a.print();

    return 0;
}

</code>

<code>
{
   selmy  ,
   lichopytnici,
   sudokopytnici
}
</code>