Large project how to seprate definition and declaration?

[Hassan Syed1]

I am new to C++ I want to define my functions declaration in a seprate header file and definitions in 2 different header files. I am saving the file with .h and .c extension in same folder where main file is located too. I also know that I have to use double quotes to include my files in main. However, I am unable to find the way to define my header file for definitions and declaration. Please give me a small example so that I can get idea about it

[leon de boer]

It should be avail able on any tutorial on the net but lets do a basic. The header file .h is where you put anything that needs to be accessed from another unit. Your functions etc are just prototype declarations. You generally put a guard #ifndef around it to stop it being included multiple times if called from multiple units. So "mycode.h" would be something like

#ifndef _MYCODE_
#define _MYCODE_

// Place public defines, structures etc here .. random couple of sample defines as example
#define DEV_OK 0 // No device error
#define DEV_ERROR -1 // Device access error

// Some prototype functions I will define in the main body file
void MyFunction1 (int someValue);
int MyFunction2 (void);

#endif

Now for the body file MyCode.cpp

#include "mycode.h" // Include your own header file

// Private internal stuff not visible outside the unit because its not in .H file

// An private integer which will just hold our function value
int CurrentValue = 0;

// Our prototype functions now get code

void MyFunction1 (int someValue){
CurrentValue = someValue; // Lets just hold value passed in
}

int MyFunction2 (void){
return (currentValue); // Just return current value
}

That is all there is to it as a minimalist code sample.

In vino veritas

[Hassan Syed1]

Sir please check the following. There is something wrong. If you correct it for or highlight any improvement factor it will be appreciated. Header File:

#ifndef _CALCULATION_H
#define _CALCULATION_H
#include "calculation.cpp"
#include "getinput.cpp"

void input_Func(void); //Input function of text.
void input_Area(void); //Input function of Area.
void input_Trap(void); //Input function of Trapezoid.
float rectangle_Area (float , float); //Declaration for Rectangle Area.
float trapezoid_Area (float , float, float); //Declaration for Trapezoid Area.

#endif

Calculation File:

#include "calculation.h"

//Calculation of Rectangle Area.
float rectangleArea (float width, float length)
{
float Area_Rectange = 0;
Area_Rectange = width * length;
return (Area_Rectange);
}

//Calculation of Trapezoid Area.
float trapezoidArea (float base1, float base2, float height)
{
float Area_Trapezoid = 0;
Area_Trapezoid = ((base1 + base2)/2) * height;
return (Area_Trapezoid);
}

Input data File:

#include "calculation.h"

//Dealing with the input and output of data
void input_Func(void)
{
cout << "\n\nEnter 1 to calculate the area of Rectangle" << endl;
cout << "Enter 2 to calculate the area of a Trapezoid" << endl;
cout << "\n\nEnter your choice : ";
cin >> choice;
}

//Dealing with input of Rectangle
float input\_Area(void)
{
    float width = 0, length = 0, answer = 0;
    cout << "Enter the width of rectangle :";
    cin >> width;
    cout << "Enter the length of rectangle :";
    cin >> length;
    answer = rectangleArea(width, length);
    cout << "The area of Rectangle is : " << answer << endl;
    break;
}

    //Dealing with input of Trapezoid.
    float input\_Trap(void)
    {
        float base1 = 0, base2 = 0, height = 0, answer = 0;
        cout << "Enter base1 of trapezoid : ";
        cin >> base1;
        cout << "Enter base2 of trapezoid : ";
        cin >> base2;
        cout << "Enter the height of trapezoid : ";
        cin >> height;
        answer  = trapezoidArea(base1, base2, height);
        cout << "The area of Trapezoid is : " << answer << endl;
        break;
    }

Main File:

/*

Name = Syed Sibt E Hassan
Registration Number = MC160201226

1. Input

[Jochen Arndt]

The problem is here:

#ifndef _CALCULATION_H
#define _CALCULATION_H
#include "calculation.cpp"
#include "getinput.cpp"
// ...

Don't include source files (*.c, *.cpp) using the include statement (especially form within header files). Also split the header file into two (or three):

• One named calculation.h with the declarations for the calculation.c source file
• One named getinput.h with the declarations for the getinput.c source file
• Optionally one named according to your project name with global declarations used by multiple source files and public declarations for your main.c source file

To build your application each source file must be compiled and the created object files must be aftwerwards linked to create the executable. This is usaully accomplished using a make file. The kind of the make file depends on your development environment. With IDE's you won't see the make file but use options to add source files to your project.

[leon de boer]

I would strengthen what Jochen said with you DON'T EVER #include *.c or *.cpp .. NOT EVER ... includes are only .H files. We allow includes to be any sort of file for historic reasons none of which we would ever advise and few programmers would even know. Please remove these lines they would never be correct anywhere much less where you have them #include "calculation.cpp" #include "getinput.cpp" So with Calculation.cpp you include its own header Calculation.H which you have done ... that's all you need the two files are then linked. If you need functions in GetInput.cpp then you include GetInput.H which will declare everything that is public from within GetInput.cpp. Do you get it that the .H file limits what you can access as a public everything else in the .CPP is hidden which is the whole point of doing it. You are trying to restrict the chance of making errors by allowing only access to the unit in the way you want. That is why you publish only what you want to allow access to on the interface of the .H file. In your case Calculation.H doesn't need to know about GetInput.cpp, even if you did need it then you include GetInput.H So if calculation.cpp needs to know about GetInput.cpp then simply include GetInput.H within calculation.cpp You seem to be over thinking it

In vino veritas

[Hassan Syed1]

Thank you everyone for your reply. Can you post in the code form like i showed in my 2nd post. If any link available about explaining this thing please share with me

[Lost User]

Header files just allow the declaration of constants, classes and functions that may be required to be used in more than one implementation file. The implementation (.c or .cpp) then includes the header file, allowing the compiler to have the declarations for any items that the C code uses. See why header files in c - Google Search[^] for further discussions on the subject.

[leon de boer]

Okay so this is your Calculation.h file ... which is only changed by removing the two include which are not needed

#ifndef _CALCULATION_H
#define _CALCULATION_H

void input_Func(void); //Input function of text.
void input_Area(void); //Input function of Area.
void input_Trap(void); //Input function of Trapezoid.
float rectangle_Area (float , float); //Declaration for Rectangle Area.
float trapezoid_Area (float , float, float); //Declaration for Trapezoid Area.

#endif

So now you must provide all that in a Calculation.cpp file which would be all the code below. So here are the functions you provided but notice I have marked the errors on the 2 functions Input_Area & Input_Trap So currently only 3 of your 5 functions are correct

#include "calculation.h" // include you header file

//Calculation of Rectangle Area.
float rectangleArea (float width, float length)
{
float Area_Rectange = 0;
Area_Rectange = width * length;
return (Area_Rectange);
}

//Calculation of Trapezoid Area.
float trapezoidArea (float base1, float base2, float height)
{
float Area_Trapezoid = 0;
Area_Trapezoid = ((base1 + base2)/2) * height;
return (Area_Trapezoid);
}

//Dealing with the input and output of data
void input_Func(void)
{
cout << "\n\nEnter 1 to calculate the area of Rectangle" << endl;
cout << "Enter 2 to calculate the area of a Trapezoid" << endl;
cout << "\n\nEnter your choice : ";
cin >> choice;
}

// YOU HAVE SERIOUS ERRORS IN THE TWO FUNCTION CODES BELOW

//Dealing with input of Rectangle
float input_Area(void) // *** ERROR *** YOUR HEADER HEADER FILE IS ==== > void input_Area(void); WHICH IS IT THEY MUST MATCH??????
{
float width = 0, length = 0, answer = 0;
cout << "Enter the width of rectangle :";
cin >> width;
cout << "Enter the length of rectangle :";
cin >> length;
answer = rectangleArea(width, length);
cout << "The area of Rectangle is : " << answer << endl;

break; // <<==== ***** ERROR ***** WHAT ARE YOU BREAKING FROM

/// ***** ERROR *****
// There is another problem here you have not returned anything
// You declare you are going to return a float and don't .. You put this === > float input_Area(void)
//
// I think you may want to return the variable Answer but your code matches
// the header file returning nothing so I am confused what you are doing
//
// You need to be clear are you returning a float or not and fix it
}

//D

[Hassan Syed1]

Can i have multiple declaration files for different functions. For example; can I have a .cpp file for having input of data and can have a separate file for calculation of data? Is it a correct approach which professional follows? Actually I am confused because of declaration and definitions in septate files. When I write whole code in main it works well as soon as put the code in separate files I started getting error. I removed the .cpp file as I told above and got that concept clear that NEVER include .cpp file in .h header file. I am still getting some function calling error. I am just 1 step away to know where the problem is coming in function call. Please someone correct that portion. i already removed the break from the function as it was mentioned and also got the logical reason behind removing it. Actually I added that break in structure but as I just copy pasted the code in functions I copied it along with it :(

[David Crow]

Hassan Syed1 wrote:

When I write whole code in main it works well as soon as put the code in separate files I started getting error.

Which means your compiler/linker options are not correct, but since you failed to share those errors, we can only guess.

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles

[leon de boer]

There Errors are explained above your header file declaration does not match your .cpp file. Even in a single file your code for Input_area and Input_trap are both bad and wrong. You will have several warnings which you are just ignoring I take it. Those warnings are real and pointing to a problem you need to fix, which becomes fatal when you turn it to a unit. You declare this in calculation.h

void input_Area(void); //Input function of Area.

You have this in your calculation.cpp

float input_Area(void){

LOOK AT THEM .. THEY ARE NOT THE SAME .. the return declare (1st word) differs ... THAT IS YOUR FIRST PROBLEM WITH THE .H FILE Again we repeat the declaration in the .H file must be EXACTLY the same as the interface actually in the .CPP file. THERE IS NO EXCEPTION TO THIS RULE .... EVER So the .H file could be changed to

float input_Area(void); //Input function of Area.

OR ... the .CPP file could be changed to

void input_Area(void){

I can't work out which definition is correct because you don't actually return anything from input_area. Either could be correct because your code has a big error I can't work out which is right. You have the same problem on float input_Trap. You declared you are returning a float but don't return anything, do you understand what I am saying when I say that????? Even in one big file you will be getting a 2 warnings, something like "function does not return value". I am struggling why you can't see the problem because you did it correctly in rectangleArea and trapezoidArea, so you know how to return a value when you declare it. So on your code you got right lets mark where you return a float.

float rectangleArea (float width, float length) // * PT1 ... HERE YOU DECLARE YOU ARE RETURNING A FLOAT .. the first word is FLOAT not VOID
{
float Area_Rectange = 0;
Area_Rectange = width * length;
return (Area_Rectange); // *** HERE YOU RETURN A FLOAT ... which is exactly what you said at PT1 ... HENCE THIS CODE IS CORRECT
}

Now look at Input_area and Input_trap the word return and some value doesn't appear in the code BUT you declared you are returning a float. The compiler and I are both confused with what you are doing. If you declare a float return, then please return one. If you don't want to return a float then change the first word on the declare to void (which matches what you have in the .H file). On the other issue yes we can mov

[Hassan Syed1]

This was the whole code from main file. Please divide it in module form like professional people do so that I can exactly see the problem in my understanding of dividing the project into moduler form

/*

Name = Syed Sibt E Hassan
Registration Number = MC160201226

1. Input from the user
2. Function Calls to reactangle and trapezoid
3. Exit loop when input is not 'Y' || 'y'
   */

#include
using namespace std;

float rectangleArea (float , float); //Declaration for Rectangle Area
float trapezoidArea (float , float, float); //Declaration for Trapezoid Area.

int main()
{
int choice = 0;
char tryagain = 0;
do
{
cout << "\n\nEnter 1 to calculate the area of Rectangle" << endl;
cout << "Enter 2 to calculate the area of a Trapezoid" << endl;
cout << "\n\nEnter your choice : ";
cin >> choice;
switch(choice)
{
//Dealing with area of Rectangle.
case 1:
{

                float width = 0.0, length = 0.0, answer = 0.0;
                cout << "Enter the width of rectangle :";
                cin >> width;
                cout << "Enter the length of rectangle :";
                cin >> length;
                answer = rectangleArea(width, length); //Function Call to Rectangle
                cout << "The area of Rectangle is : " << answer << endl;
                break;
            }

                     //Dealing with area of Trapezoid.
        case 2:
            {

                float base1 = 0.0, base2 = 0.0, height = 0.0, answer = 0.0;
                cout << "Enter base1 of trapezoid : ";
                cin >> base1;
                cout << "Enter base2 of trapezoid : ";
                cin >> base2;
                cout << "Enter the height of trapezoid : ";
                cin >> height;
                answer  = trapezoidArea(base1, base2, height); //Function Call to Trapezoid
                cout << "The area of Trapezoid is : " << answer << endl;
                break;
            }

        default:{
            cout << "Neither 1 nor 2 entered." << endl;
            }
        }

        cout << "\\n Do you want to do another calculation? : ";
        cin >> tryagain;
    }while (tryagain == 'Y' || tryagain == 'y');

return

[David Crow]

How hard is it to put the function signatures in a .h file and the functions themselves in a .c file? Then you just need an additional #include directive, and an adjustment to the make file.

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles

[leon de boer]

You are not thinking like a programmer ... at the moment your answers are not needed as you just display them to the console So one easy option to patch your code in Calculation.CPP is this

void input_Area(void) // ** Pt1 here you declare you are going to return nothing AKA a void
{
float width = 0, length = 0, answer = 0;
cout << "Enter the width of rectangle :";
cin >> width;
cout << "Enter the length of rectangle :";
cin >> length;
answer = rectangleArea(width, length);
cout << "The area of Rectangle is : " << answer << endl;
}

That matches your .H header file you don't have to change anything

#ifndef _CALCULATION_H
#define _CALCULATION_H

void input_Func(void); //Input function of text.
void input_Area(void); //Input function of Area. **** FIXED NOW MATCHES THE .CPP file
void input_Trap(void); //Input function of Trapezoid. *** STILL BUGGED .CPP says it returns a float this says void
float rectangle_Area (float , float); //Declaration for Rectangle Area.
float trapezoid_Area (float , float, float); //Declaration for Trapezoid Area.

#endif

So you could go and fix input_Trap in the same way I am leaving that as an exercise .. problem fixed. So there is another alternative which is to return the answer in Calculation.cpp

float input_Area(void) // ** Pt1 here you declare you are going to return a float
{
float width = 0, length = 0, answer = 0;
cout << "Enter the width of rectangle :";
cin >> width;
cout << "Enter the length of rectangle :";
cin >> length;
answer = rectangleArea(width, length);
cout << "The area of Rectangle is : " << answer << endl;

return (answer); // * So return the answer like you said you would at Pt1
}

Now you need to fix the header file Calculation.H

#ifndef _CALCULATION_H
#define _CALCULATION_H

void input_Func(void); //Input function of text.
float input_Area(void); //Input function of Area. **** FIXED NOW MATCHES THE .CPP file above
void input_Trap(void); //Input function of Trapezoid. *** STILL BUGGED .CPP says it returns a float this still says void
float rectangle_Area (float , float); //Declaration for Rectangle Area.
float trapezoid_Area (float , float, float); //Declaration for Trapezoid Area.

#endif

So you could go and fix input_Trap in the same way I am leaving that as an exercise .. problem fixed again. Look carefully at both answers all that changed is whether you return answer or not. In both cases the .H f

[leon de boer]

Your code is not in a fit state to put in modules .. however I have provided code that does roughly what you want in modules. The code includes error checks on the entry you don't do in any way. File: Calculation.H

#ifndef _CALCULATION_H
#define _CALCULATION_H

float RectangleArea (float width, float length);
float TrapezoidArea (float base1, float base2, float height);

#endif

File: Calculation.CPP

#include "Calculation.h"

//Calculation of Rectangle Area.
float RectangleArea(float width, float length)
{
float Area_Rectange;
Area_Rectange = width * length;
return (Area_Rectange);
}

//Calculation of Trapezoid Area.
float TrapezoidArea(float base1, float base2, float height)
{
float Area_Trapezoid;
Area_Trapezoid = height * (base1 + base2) / 2;
return (Area_Trapezoid);
}

File: Input.H

#ifndef _INPUT_H
#define _INPUT_H

/* Asks user for menu choice up to given max value */
unsigned int MenuInput (char* prompt, unsigned int maxNum);

/* Asks user for a float within given range, with prompt text */
float GetFloatInput(char* prompt, float min, float max);

#endif

File: Input.CPP

#include #include "input.h"

/* Asks user for menu choice up to given max value */
unsigned int MenuInput(char* prompt, unsigned int maxNum) {
bool validFlag = false;
unsigned int iResult;
do {
printf(prompt); // Put prompt on screen
int err = scanf_s("%u", &iResult); // Scan for a unsigned int and hold any error
if ((err == 0) || (iResult > maxNum)) { // Check value between 0 .. maxNum
printf("Invalid menu choice try again\n"); // If value is invalid .. prompt that
} else validFlag = true; // Value is valid
scanf_s("%*[^\n]"); // Make sure we dump any characters in buffer
} while (validFlag == false); // Loop until valid
return (iResult); // Return result
}

/* Asks user for a float within given range, with prompt text */
float GetFloatInput (char* prompt, float min, float max) {
int err;
float fResult;
do {
printf(prompt); // Put prompt on screen
err = scanf_s("%f", &fResult); // Scan for a float and hold any error
if (err == 0) { // Err = zero means entry is not a float
printf("Entry is not a float try again\n"); // Prompt entry was not a float to screen
} else {
if (fResult < min) { // Check entry is above minimum
printf("Re-enter value below minimum of %f\n", min);// Prompt

[Hassan Syed1]

even your code giving error. Have a look at screenshot please. However, Thank you for showing me the correct way to code. I got many point out of it. Screen Shot of Error = http://i64.tinypic.com/16m0zr4.jpg

[leon de boer]

Something funky with GCC compiler but easy to fix include float.h ... its doesn't know what FLT_EPSILON, FLT_MAX are. These are standard C++ Macro constant definitions so you can just look it up (float.h) - C++ Reference[^] So top of Source.CPP becomes

#include
#include // Added to define FLT_EPSILON & FLT_MAX
#include "calculation.h"
#include "input.h"
using namespace std;

In vino veritas

[Hassan Syed1]

More errors :( Thank you for your guidence at least i am learning new things. Screen Shot = http://i65.tinypic.com/ncjddc.jpg[^]

[leon de boer]

That one is you ... It is basically telling you it can't find the code for GetFloatInput. GetFloatInput is defined in Input.H and Input.CPP which are included see here

#include
#include "calculation.h"
#include "input.h" // <----- GetFloatInput is defined in this include>
using namespace std;

So we are down to either a typo error or you haven't included Input.CPP into your source files. I assume you cut and paste so unlikely to be a typo so lets try number two. Did you use the menu system and do .... Project... Add files... to add the new .H and .CPP to your source files to the project? I don't use code blocks but it will be something like that. Can I ask you to show me the line about the deprecated string function points to .. I am interested to see what GCC is complaining about. There is possibly another warning you are going to get on the definition of main in Source.CPP can you change it from int main() to

int main(int argc, char**argv)

That is the technically correct definition, not the Microsoft shorthand I used.

In vino veritas

[Hassan Syed1]

Excellent. Working fine now however I have to remove scanef_s. that _s was creating problem so i only remove _S and scanef remain as it. Now code working fine. Thank you for ur guidance. Now i got the clear idea how to write the code. I will copy the way you wrote this code. I am not a bad student however I like programming but problem is I think i am unable to think like a programmer. I am trying hard for that but no success yet :( I want to excel in this field but sometimes I stuck :((