error when i using a function in a class in cpp

[dizgah]

hi every body
in a cpp file i include a header file and want to use header file's functions inside class but it shows a error:

    lib1.h
    class class_x{
    public:
    calss_x();
    private:

    }

---

    lib1.cpp
    #include "lib1.h"
    #include "header1.h"
    class_x::class_X()
    {
    function_of_header1.h();
    }

error shows undefine symbol function_of_header1.h()
whas matter?
WBR

 

[horace1]

where is function_of_header1() decalared? in header1.h ?
what is the header1.h code?
note you cannot have a . in an identifier name such as function_of_header1.h()

should it be something like

//lib1.h
    class class_x{
    public:
    class_x();
    private:
    };

// header1.h
    void function_of_header1()
    {
    //
    }

   //lib1.cpp
    #include "lib1.h"
    #include "header1.h"
    class_x::class_x()
    {
    function_of_header1();
    }