Two problems in this C program?

Question

I'm not sure where I went wrong, currently there are two problems:
1. When I press Cube or cylinder, it displays the word "cube" or "cylinder" but then takes me back to the "box" option
2. When I compute the digits for box there's alway an error at the end (before it give me the answer).

#include "simpio.h"
#include "genlib.h"
#include
#include
#include
#define strEqual

main()
{
string option;
int box, cylinder, cube, x, y, z, vol, pi;
pi=3.1415926;
printf("Enter 'box', 'cylinder', or 'cube'\n");
option=GetLine();

if (strEqual(option, "box"))
{
printf("For box:\n");
printf("Enter the first side of the box:\n");
x=GetInteger();
printf("Enter the second side of the box:\n");
y=GetInteger();
printf("Enter the height of the box:\n");
z=GetInteger();
vol =(x*y*z);
printf("Volume of the box is %s\n", vol);
}


else if (strEqual(option, "cube"))
{
printf("For cube\n");
printf("Enter the side of the cube:\n");
x=GetInteger();
vol = (x*x*x);
printf("Volume of the cube is %d\n",vol);
}



else if (strEqual(option, "cylinder"))
{
printf("For cylinder:\n");
printf("Enter the diameter of cylinder:\n");
x=GetInteger();
printf("Enter the length of the cylinder:\n");
y=GetInteger();
vol=(x * x* pi / (4 * y));
printf("Vomlume of the cylinder is %d\n",vol);
}

system("pause");
}

Answer 1

This is a subtle one in two ways. When you #define strEqual this way:



#define strEqual



you're setting the compile-time variable "strEqual" to an empty string (the value after strEqual). A normal #define does something like this:



#define strEqual strcmp



Thus, when you make those tests, say



if (strEqual(option, "box"))



the C preprocessor substitutes an empty string for strEqual, producing this code for the compiler:



if ( (option, "box" ))



In other words, instead of a C function call, you have a sequential evaluation statement. C allows this, but uses as the value of the statement the value of the last element in it. In this case, that's the address of "box". Since this is a non-zero value, the if( ) statement takes that as a true value and executes the code inside the if clause.



The trouble all lies in that #define. As it's being used, it has to define strEqual AS something.



Hope that helps.

Answer 2

There's a number of issues here. vol and pi should be declared as doubles (or you can include and use M_PI, the pi constant). You should be using %d instead of %s when you print the "Volume of the box." Also, you should check to make sure you understand what strEqual() returns when the string matches. strcmp, a similar function, returns 0 on a match, which is evaluated as FALSE. If that's not your problem, make sure you're not getting a new-line character in your call to GetLine() (you could be getting "box\n" instead of just "box", which wouldn't match any of your options).



Good luck.

Answer 3

First change the declaration of "vol" and "pi" variables to float or double because they includes points.

may be while computing vol variable the size increases the integer size

i.e. -32768 to 32767 in C



"then takes me back to the "box" option"

What do you mean by this as i know u r not using loop then why box option again.

Answer 4

Why did u declared pi as int and then maked it equal to a float value?I don't know much C,but i cand write the progr for u in cpp.