Having trouble with a header file i created

[kip2847]

i keep getting an error for some reason
Am using c++ 4.9.9.2
here is my complie log:
Compiler: Default compiler
Building Makefile: "C:\Dev-Cpp\Makefile.win"
Executing make...
make.exe -f "C:\Dev-Cpp\Makefile.win" all
g++.exe -c inventorymain.cpp -o inventorymain.o -I"C:/Dev-Cpp/lib/gcc/mingw32/3.4.2/include" -I"C:/Dev-Cpp/include/c++/3.4.2/backward" -I"C:/Dev-Cpp/include/c++/3.4.2/mingw32" -I"C:/Dev-Cpp/include/c++/3.4.2" -I"C:/Dev-Cpp/include"

In file included from inventorymain.cpp:5:
funct: In function void input_sku()': funct:7: error:sku' undeclared (first use this function)

funct:7: error: (Each undeclared identifier is reported only once for each function it appears in.)
funct:10: error: cout' undeclared (first use this function) funct:17: error:cin' undeclared (first use this function)

inventorymain.cpp: At global scope:
inventorymain.cpp:6: error: `define' does not name a type

inventorymain.cpp: In function int main(int, char**)': inventorymain.cpp:16: error:cout' undeclared (first use this function)
inventorymain.cpp:20: error: `cin' undeclared (first use this function)

make.exe: *** [inventorymain.o] Error 1

Execution terminated

here is my program:
[main.cpp]

include <cstdlib>

include <iostream>

include <limits>

include <ios>

include "funct.h"

double sku[1500];
using namespace std;

int main(int argc, char argv[])
{
int choice =0;
while (choice != 8 )
{
cout << "\t Please Choose an Option from the List: \n";
cout << "\t \t 1 - Scan in SKU. \n" ;
cout << "\t \t 2 - Compile Scanned items. \n" ;
cout << "\t \t 8 - Quit Program. \n" ;
cin >> choice;
if(cin.fail())
{
system("cls");
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
cout << " \t \t Please enter a valid character* \n";
}
if( choice >= 9 || choice < 0)
{
system ("cls");
cout << "This is not one of the options \n";
}
if (choice == 1)
input_sku();
}
system("PAUSE");
return EXIT_SUCCESS;
}

[funct.h]

void input_sku ()
{
system("cls");
int i= 0;
sku[i] =0;
while ( i < 1499 && sku[i] != 9999)
{
cout << "Please Enter Sku of items: \nWhen Done Enter 9999: \n";
if (sku[i] < 999999999) // set range of sku
{
cout << "Plese Enter a Sku in Range \n ";
}
else
++i;
cin >> sku [i];
system ("cls");
}
}

[Osito]

It's kind of strange to put functions in a header file, but I guess it's not illegal. I would consider it bad practice, but I'm no expert. Regardless, the function in the header file can't access a variable that is defined after the header file is included. Likewise, the function can't assume namespace std is being used if your "using namespace std" line occurs after the header file is included.

[kip2847]

um i dont understand ur answer... mind clearifying?

[Osito]

Sorry, not sure how to make that more clear. Maybe someone else can help.

[Kurgusov]

Hi kip...

I think what you'd need to do is declare sku [ 1500 ] as extern to your header file ( ideally this would give it scope to your headers .cpp file),

so near the top of your header file add

extern double sku [ 1500 ] ;

outside of any function.

This would give that headers associated source file access to sku[].

Do you have a .cpp file named the same as the header?

eg aheader.h and also aheader.cpp ?

Also have you included iostream in your header, giving scope to std::cout and all.

[Kurgusov]

multiple files caused me soo much grief until Clifford put my wrongs to rights.

Its really very easy and goes like this....

an example...

ifndef AHEADER_H
define AHEADER_H

//put function prototypes here
//put external variables here as in extern int avariable ;
//#include other header files whos functions/variables need to be used within this file
//code class's/structure's here

endif

now you create a new file and save it as AHEADER.cpp

Inside this source file you define the functions/methods and assign values to your variables declared in the files header.

eg...

//header

int sum ;

//headers .cpp file

sum = 0 ;

I hope that helps a bit, it took me ages to get multiple files working together.

[Anonymous]

Header file inclusion is not any kind of magic, it simply replaced the #include with the content of teh header file before compilation, so you have

include "funct.h"

double sku[1500];
using namespace std;

but funct.h uses sku[]... before it is declared in main.h. It also uses std:: symbols without scope resolution.

Furthermore there is something very strange about this build. You talk about files "main.cpp" and "funct.h", but the log refers to "inventorymain.cpp" and "funct" (with no extension). And you have teh error message:
inventorymain.cpp: At global scope:
inventorymain.cpp:6: error: `define' does not name a type

... but there is no symbol 'define' in this code - certainly not on line 6. You really do have to post the code to which the log refers!

Anyway, that is why you get the errors, but the code is an abuse of the header file mechanism. Header files should include declarative (in C++ inline) code only - no function definitions. Funct.h should merely contain:

---

if !defined FUNCT_H

define FUNCT_H

extern double sku[]
extern void input_sku() ;

endif

---

Then you have an additional file funct.cpp

---

include <cstdlib>

include <iostream>

include "funct.h"

using namespace std;

void input_sku()
{
...
}

---

You then need to use Dev-C++ project tool (always a good idea anyway) - File->New->Project, so that you can add multiple sources to your build.

There are all sorts of other problems with this, but that is the main issue. You should not put your project in c:\dev-cpp\ as you have done. For starters it is 'polluting' the installation. Projects should have their own folder - what will happen when you create a second project? It will screw up the build of this one - perhaps that's how come the log and the code do not match!? Never create projects under c:\dev-cpp\ or a subfolder of that in any case, there is a bug in Dev-C++ that sometimes causes builds to fail when you do that.

Your input loop never allows you to enter a value for sku[4999] (the last element) - was that intentional?

Finally let's not get into the rights and wrongs of global data at the moment, but currently sku is declared in main.cpp, but never used. It could be statically declared in funct.cpp, where all functions that access it could reside. This 'data hiding' approach is better done in C++ using a class.

Clifford.

[Kurgusov]

2 more things since Im lonely and its sunday.

its #ifndef...#define...

remember to include the hash sign.

and a great tip (i think)..

whenever you overcome a problem write down the error message the compiler gives and also the solution,
very soon youll have a manual you can sell off for profit.