[PsychoCoder]

Topics merged, please no more duplicates

[jjl]

you should read up on c++ control flow basics. You cannot seperate conditions with a comma ',', for example this is wrong

if(a == 1, b == 2) //wrong!

There are two different operators to accomplish this,

|| or
&& and

if(a == 1 || b == 2) //if a == 1 or b == 2 then execute 

if(a == 1 && b == 2) //if a ==1 and b == 2 then execute

When checking conditions you use the comparison operator == not the assignment operator.

the comparison operator == returns a boolean value, true or false. The assignment operator does not have a return value it will always execute

int x = 5;
int y = 10;

if(x = y) //this will always execute, your not comparing anything.. your assigning
{
    //now x = y
}

you need to use the comparison operator

int x = 5;
int y = 10;

if(x == y) //notice the comparison operator ==
   cout<<"X EQUALS Y"<<endl;
else //do not equal
   cout<<"NOT EQUAL"<<endl;

This post has been edited by ImaSexy: 23 June 2010 - 08:51 AM

[eZACKe]

I suggest including more spaces between your lines. That, and proper indentation will make it much easier for you to read and debug.

One you make those changes and do what ImaSexy has commented on, you should easily be able to get this program working like you want.

If after you make those changes it's still not working, post the updated code on here and we'll take a look.

[jjl]

heres the logic for an if statment,

if the condition is true, execute code beween brackets

if  ( x == 1 )//if this is true
{
    //execute code within these brackets
}

Dont try to put all of your code within the conditions of your if statment

[eZACKe]

Let's take a look at this part of your code now that I've deciphered what you are trying to say:

 if  (( x == 1 && cout << " please enter the value of speed of light : " &&
       cin >> speed_of_light && cout << " \n " << " please enter the distance: "
       && cin >> distance ) || ( x == 0 && speed_of_light = 300000000));

What I think you're trying to say here is:

If x(the value the user enters at the beginning about whether or not he wants to choose a speed of light) is equal to 1....

 if  (( x == 1//this is your code, you should change it to if(x ==1)

...then you want to allow the user to enter the values.

cout << " please enter the value of speed of light"
cin >> speed_of_light
cout << " \n " << " please enter the distance:"
cin >> distance

ELSE IF x is equal to 0 (you put || where there should be an else-if)....

speed_of_light = 300000000

Just remember, after if-statements there should be brackets({ }) that have everything inside of them that goes in that part. And then there should also be brackets for the else-if and have everything that goes in there.

[v0rtex]

Here is what I think you were looking for:

#include <iostream>

using namespace std;

int main()
{
      double speed_of_light,distance,time ;
      bool x ; 
//1 = TRUE, 0 = FALSE
       cout << "please note all data in units of SI" << " \n"<< " would you like to enter the value of speed of light ?" << " \n" << "reply in 1 for yes and 0 for no "   ;
       cout << " \n " ; cin >> x ;
    if  ( x == 1)  //if int x is equal to 1, execute body
       { 
            //body:
       cout << " please enter the value of speed of light : "; 
       cin >> speed_of_light;
       cout << " \n " << " please enter the distance:";
       cin >> distance;
       }
       else if ( x == 0 ) //if x is equal to 0, then execute statement below:
       speed_of_light = 300000000;
       /*if no braces are included then only the next statement will 
       be executed as part of the if statement, in this case, that is sufficient
       */  
       cout << " the time needed is :" << time ;
      cin.ignore ( 256 , '/n' );
      cout << " press enter to continue " << endl ;
      cin.get () ;
    return 0;
}

This post has been edited by v0rtex: 24 June 2010 - 01:46 AM

[eZACKe]

Glad I could be of assistance!