C++ multiple definition first defined here -

i'm typing out example program absolute c++ , keeps giving me error:

/tmp/ccjfp4dm.o: in function `hashtablesavitch::hashtable::hashtable()': hashtableimp.cpp:(.text+0x0): multiple definition of `hashtablesavitch::hashtable::hashtable()' /tmp/cchuzlfl.o:hashtable.cpp:(.text+0x0): first defined here /tmp/ccjfp4dm.o: in function `hashtablesavitch::hashtable::hashtable()': hashtableimp.cpp:(.text+0x0): multiple definition of `hashtablesavitch::hashtable::hashtable()' /tmp/cchuzlfl.o:hashtable.cpp:(.text+0x0): first defined here /tmp/ccjfp4dm.o: in function `hashtablesavitch::hashtable::~hashtable()': hashtableimp.cpp:(.text+0x16): multiple definition of `hashtablesavitch::hashtable::~hashtable()' /tmp/cchuzlfl.o:hashtable.cpp:(.text+0x16): first defined here /tmp/ccjfp4dm.o: in function `hashtablesavitch::hashtable::~hashtable()': hashtableimp.cpp:(.text+0x16): multiple definition of `hashtablesavitch::hashtable::~hashtable()' /tmp/cchuzlfl.o:hashtable.cpp:(.text+0x16): first defined here /tmp/ccjfp4dm.o: in function `hashtablesavitch::hashtable::~hashtable()': hashtableimp.cpp:(.text+0x44): multiple definition of `hashtablesavitch::hashtable::~hashtable()' /tmp/cchuzlfl.o:hashtable.cpp:(.text+0x44): first defined here /tmp/ccjfp4dm.o: in function `hashtablesavitch::hashtable::computehash(std::string)': hashtableimp.cpp:(.text+0x6a): multiple definition of `hashtablesavitch::hashtable::computehash(std::string)' /tmp/cchuzlfl.o:hashtable.cpp:(.text+0x6a): first defined here /tmp/ccjfp4dm.o: in function `hashtablesavitch::hashtable::containsstring(std::string) const': hashtableimp.cpp:(.text+0x7a): multiple definition of `hashtablesavitch::hashtable::containsstring(std::string) const' /tmp/cchuzlfl.o:hashtable.cpp:(.text+0x7a): first defined here /tmp/ccjfp4dm.o: in function `hashtablesavitch::hashtable::put(std::string)': hashtableimp.cpp:(.text+0x8e): multiple definition of `hashtablesavitch::hashtable::put(std::string)' /tmp/cchuzlfl.o:hashtable.cpp:(.text+0x8e): first defined here collect2: error: ld returned 1 exit status makefile:2: recipe target 'hashtable' failed make: *** [hashtable] error 1 

i've reduced program down pure basics still can't figure out what's going on. can help?

makefile:

hashtable: listtools.h listtools.cpp hashtable.h hashtable.cpp hashtableimp.cpp      g++ listtools.h listtools.cpp hashtable.h hashtable.cpp hashtableimp.cpp -o hashtable 

hashtable.h

#ifndef hashtable_h #define hashtable_h  #include <string> #include "listtools.h"  using linkedlistsavitch::node; using std::string;  namespace hashtablesavitch {     const int size = 10;     class hashtable {     public:         hashtable();         virtual ~hashtable();         bool containsstring(string target) const;         void put(string s);     private:         node<string> *hasharray[size];         static int computehash(string s);     }; }  #endif 

hashtable.cpp

#include <string> #include "listtools.h" #include "hashtable.h"  using linkedlistsavitch::node; using linkedlistsavitch::search; using linkedlistsavitch::headinsert; using std::string;  namespace hashtablesavitch {     hashtable::hashtable() {      }      hashtable::~hashtable() {      }      int hashtable::computehash(string s) {         return 0;     }     bool hashtable::containsstring(string target) const {         return true;     }      void hashtable::put(string s) {      } } // hashtablesavitch 

hashtableimp.cpp

#include <string> #include <iostream> #include "hashtable.h" #include "listtools.cpp" #include "hashtable.cpp" using std::string; using std::cout; using std::endl; using hashtablesavitch::hashtable;  int main() {     hashtable h;     cout << "adding cat, dog, turtle, , bird" << endl;     h.put("cat");     h.put("dog");     h.put("turtle");     h.put("bird");      cout << "contains cat? " << h.containsstring("cat") << endl;     cout << "contains dog? " << h.containsstring("dog") << endl;     cout << "contains turtle? " << h.containsstring("turtle") << endl;     cout << "contains bird? " << h.containsstring("bird") << endl;     cout << "contains cow? " << h.containsstring("cow") << endl;     cout << "contains fish? " << h.containsstring("fish") << endl;      return 0; } 

listtools.h

#ifndef listtools_h #define listtools_h  namespace linkedlistsavitch {     template<class t>     class node {     public:         node(const t& thedata, node<t>* thelink) : data(thedata), link(thelink) {}         node<t>* getlink() const {return link;}         const t getdata() const {return data;}         void setdata(const t& thedata) {data = thedata;}         void setlink(node<t>* pointer) {link = pointer;}     private:         t data;         node<t> *link;     };      template<class t>     void headinsert(node<t>*& head, const t& thedata);      template<class t>     void insert(node<t>* afterme, const t& thedata);      template<class t>     void deletenode(node<t>* before);      template<class t>     void deletefirstnode(node<t>*& head);      template<class t>     node<t>* search(node<t>* head, const t& target); } // linkedlistsavitch  #endif 

you should not #include cpp's main hashtableimp.cpp, if want list them on g++ command line.

actually have 2 options here:

• include all code 1 file (or split code several files , #include 1 another, 1 file) — in such case need list main file in g++ command line
• really split code across several files — list these files on g++ command line, not need #include files definitions (usually cpp) other files.

the reason one definition rule: function (with exceptions) should defined in 1 place in whole program. if #include 1 cpps anothers, , compile of them, repeat definitions.

usually former approach used small programs, , latter lager projects. more commonly, in latter approach compile each file 1 one, , link them together.

also note not need list .h files in command line, should not compiled themself, #included other .cpp files compiler knows declaration of functions/objects/etc used there.