Simple Calculator: Not Positive About Correct Usage of C++

Dear Fellow C++ Programmers,

I am currently just producing a simple scientific calculator to improve and refresh my memory on some skills (I'm a novice programmer). - I am not sure if what I wrote is legal, such as declaring a function from a class outside of the function (you will see). I tried to space out my coding nicely and added comments where my problems are. If anyone could provide aid I would very much appreciate it - thank you!

Code:

#include <iostream.h>
#include <stdlib.h>
int main() {

//global variables
char choice;
int ammount;
float a;
float b;
float c;
float answer;

//class containing functions to be created...
class op_function; {
op_add();
op_sub();
op_mul();
op_div();
op_sqr();
op_sqr_root();
op_pi();
op_sin();
op_cosin();
op_tan();
op_sci_notate();
op_retansw();
}

          //main menu
          cout << "Scientific Calculator Version 0.1 /n";
          cout << "[01] Addition /n";
          cout << "[02] Subtraction /n";
          cout << "[03] Multiplcation /n";
          cout << "[04] Division /n";
          cout << "[05] Square /n";
          cout << "[06] Square Root /n";
          cout << "[07] Circle /n";
          cout << "[08] Sin - Cosin - Tangent /n";
          cout << "[09] Scientific Notation /n";
          cout << "[10] Formulae /n";
          cout << "[10] About Information /n";
          cout << "Selection # ["

          cin >> choice

          cout << "] /n";

          switch(choice) {

                         //case '01' is the selection for addition
                         //case '01' contains 1 overloaded function
                         case '01':

                              cout << "Addition Version 0.1 /n";
                              cout << "Supported: Three Floating Pnts. /n"
                              cout << "Specify Number Ammount: ";

                              cin >> ammount;

                                  //does this first if statement go with the last else statement?
                                  if (ammount == 1) {
                                     cout << "Cannot Compute Value w/ One Number"; }

                                  if (ammount == 2) {

                                     cout << "Enter Num(1): ";

                                     cin >> a;

                                     cout << "/n";
                                     cout << "Enter Num(2): ";

                                     cin >> b;

                                     //do I specify the decleration here? or in the class structure?
                                     op_function.op_add(float a, float b);

                                     op_function.op_add() {
                                              return a + b; }

                                     answer = op_function.op_add(a, b);

                                     cout << "Answer: = " answer;

                                  else {

                                     cout << "Enter Num(1): ";

                                     cin >> a;

                                     cout << "/n";
                                     cout << "Enter Num(2): ";

                                     cin >> b;

                                     cout << "/n";
                                     cout << "Enter Num(3): ";

                                     cin >> c;

                                     //do I specify this here or in the class structure?
                                     op_function.op_add(float a, float b, float c);

                                     op_function.op_add() {
                                              return a + b + c; }

                                     answer = op_function.op_add(a, b, c);

                                     cout << "Answer: = " answer; }

                                  else {
                                     cout << "Cannot Compute Value w/ One Number"; }

                                  //Rest Is Unfinished

I am trying to maintain clean and professional looking code for my own reference and skill and in situations such as these. I hope it is clear enough to understand - if not, I guess i'll still be tinkering with it.

Your class and global variable definitions should be outside of main( ), and its not className; { ... }, its className {...};

Oof! Yes that was a grave mistake - nothing that couldn't be quickly fixed. - I made some changes while I was waiting for a reply and many things are comming back to me. - I am running into only "parse" errors now (for those of you who have Bloodshed DevC++) - Everything seems to be in order but I have a feeling it has to do with the op_function.op_add(a, b) bit... heres the modified coding.

Code:

#include <iostream.h>
#include <stdlib.h>

char choice;
int ammount;
float a;
float b;
float c;
float answer;

class op_function {
public:
float op_add(float a, float b, float c);
float op_sub();
float op_mul();
float op_div();
float op_sqr();
float op_sqr_root();
float op_pi();
float op_sin();
float op_cosin();
float op_tan();
float op_sci_notate();
float op_retansw();
};

int main() {

          cout << "Scientific Calculator Version 0.1 /n";
          cout << "[01] Addition /n";
          cout << "[02] Subtraction /n";
          cout << "[03] Multiplcation /n";
          cout << "[04] Division /n";
          cout << "[05] Square /n";
          cout << "[06] Square Root /n";
          cout << "[07] Circle /n";
          cout << "[08] Sin - Cosin - Tangent /n";
          cout << "[09] Scientific Notation /n";
          cout << "[10] Formulae /n";
          cout << "[10] About Information /n";
          cout << "Selection #: ";

          cin >> choice;

          cout << "/n";

          switch(choice) {

                         case '1':

                              cout << "Addition Version 0.1 /n";
                              cout << "Supported: Three Floating Pnts. /n";
                              cout << "Specify Number Ammount: ";

                              cin >> ammount;

                                  if (ammount == 1) {
                                     cout << "Cannot Compute Value w/ One Number"; }

                                  if (ammount == 2) {

                                     cout << "Enter Num(1): ";

                                     cin >> a;

                                     cout << "/n";
                                     cout << "Enter Num(2): ";

                                     cin >> b;

                                     op_function.op_add(a, b) {
                                              return a + b; };

                                     answer = op_function.op_add(a, b);

                                     cout << "Answer: = " answer;

                                  else {

                                     cout << "Enter Num(1): ";

                                     cin >> a;

                                     cout << "/n";
                                     cout << "Enter Num(2): ";

                                     cin >> b;

                                     cout << "/n";
                                     cout << "Enter Num(3): ";

                                     cin >> c;

                                     op_function.op_add(a, b) {
                                              return a + b + c; }

                                     answer = op_function.op_add(a, b, c);

                                     cout << "Answer: = " answer; }

                                  else {
                                     cout << "Cannot Compute Value w/ One Number"; }

I think the problem lies in the op_function accessing the op_add. Do I need to access op_add() through op_function since I placed it in its class?

You need to create an intstance of op_function.

Code:

op_function opfun;
float x = opfun.op_add( 1, 2, 3 );

Parse errors! There attacking! Grr... no more errors with the calling of the function and return types... now just inconvienant parse errors that i'm about to blow a fuse at - everything seems in order - I checked syntax but I am sure I missed something =( take a look...

Code:

#include <iostream.h>
#include <stdlib.h>

char choice;
int ammount;
float a;
float b;
float c;
float d;
float answer;

class op_function {
public:
float op_add(float, float, float);
float op_add(float, float);
float op_sub();
float op_mul();
float op_div();
float op_sqr();
float op_sqr_root();
float op_pi();
float op_sin();
float op_cosin();
float op_tan();
float op_sci_notate();
float op_retansw();
};

int main() {

op_function op_funct;

          cout << "Scientific Calculator Version 0.1 /n";
          cout << "[01] Addition /n";
          cout << "[02] Subtraction /n";
          cout << "[03] Multiplcation /n";
          cout << "[04] Division /n";
          cout << "[05] Square /n";
          cout << "[06] Square Root /n";
          cout << "[07] Circle /n";
          cout << "[08] Sin - Cosin - Tangent /n";
          cout << "[09] Scientific Notation /n";
          cout << "[10] Formulae /n";
          cout << "[10] About Information /n";
          cout << "Selection #: ";

          cin >> choice;

          cout << "/n";

          switch(choice) {

                         case '1':

                              cout << "Addition Version 0.1 /n";
                              cout << "Supported: Three Floating Pnts. /n";
                              cout << "Specify Number Ammount: ";

                              cin >> ammount;

                                  if (ammount == 1) {
                                     cout << "Cannot Compute Value w/ One Number"; }

                                  if (ammount == 2) {

                                     cout << "Enter Num(1): ";

                                     cin >> a;

                                     cout << "/n";
                                     cout << "Enter Num(2): ";

                                     cin >> b;

                                     op_funct.op_add(a, b) { //Parse Error Before '{'
                                              return a + b; };

                                     answer = op_funct.op_add(a, b, c);

                                     cout << "Answer: = " << answer;

                                  else { //Parse Error Before 'else'

                                     cout << "Enter Num(1): ";

                                     cin >> a;

                                     cout << "/n";
                                     cout << "Enter Num(2): ";

                                     cin >> b;

                                     cout << "/n";
                                     cout << "Enter Num(3): ";

                                     cin >> c;

                                     op_funct.op_add(a, b, c) { //Parse Error Before '{'
                                              return a + b + c;


                                     answer = op_funct.op_add(a, b, c);

                                     cout << "Answer: = " << answer; }

                                  else { //Parse Errior Before 'else'
                                     cout << "Cannot Compute Value w/ One Number"; }
                                     break;
                                     return(0); }

ahhh parse errors! ><

'choice' is a single char but you have two chars to make '10'. Use an int instead like this:

int choice = 0;
cin >> choice;
switch(choice) {
case 1:
//do something
break;
case 2:
//do something
break;
default: // nothing for now
}


You need a '}' before the else statement to close the if statement.

And what's this? a function definition right smack down the middle of another (main() in this case)?

op_funct.op_add(a, b) { //Parse Error Before '{'
return a + b; };

Functions must be defined separately.

Thanks so much! - right now doing some homework that is in need to be finished, - i'll hop right on after, and follow the same proccess for each function, define first, than execute. Is this correct?

//define first
op_add(a, b) {
return a + b;

/*
Get values for a and b here
*/

//enter and execute function
op_funct.op_add()

//print to screen answer
cout << op_add();