/* An example on the use of functions:
    function with a single return       file: 5ex1.cpp
   FALL 1998
   ___________________________________
   Jacob Y. Kazakia   jyk0
   October 4, 1998
   Example 1 of week 5
   Recitation Instructor: J.Y.Kazakia
   Recitation Section  01
   ___________________________________
 
Purpose: This program uses a function
named volume to calculate the various partial volumes of a
composite solid body. The body consists of a cylinder of
radius R and height hcyl and a cone of height hcon 
ymmetrically sitting on top of the cylinder
and having a base of the same radius as the cylinder.
 
  The function has the following arguments:
 a)  The radius of the base  ( in meters )
 b)  The height hcyl  ( in meters )
 c)  The height hcon  ( in meters )
 d)  an integer choice which takes the values 1, 2, 3
     for 1, the function returns the volume of the cylindrical
            part only.
     for 2, the function returns the volume of the conical
            part only.
     for 3, the function returns the total volume.
 
 
   Algorithm:   The volume of the cylinder is calculated by
 
                 vcyl = PI * radius^2 * hcyl
 
                The volume of the cone is calculated by
 
                 vcon = (1/3 ) PI * radius^2 * hcon
 
  Here PI is a constant set equal to 3.14159265358979
 
                */
 
#include <iostream.h>

// Prototype the function
 
float volume ( int choice, float radius, float hcyl, 
               float hcon );
 

//  Define the constant pi
 
const float PI = 3.14159265358979 ;
 
void main()
{
 
// declare the variables of the main function
 
int m ;    // integer to be used for choosing mode
float r ;  // the radius
float h1 ; // the height of the cylinder
float h2 ; // the height of the cone
float v_cyl, v_con, v_total ;  // the volumes
 
//  "hard code" the variables
 
r  = 2.34 ; // meters
h1 = 1.12 ; // meters
h2 = 3.12 ; // meters

// calculate volumes   by invoking the function
 
v_cyl = volume(1, r, h1, h2);
 
v_con = volume(2, r, h1, h2);
 
v_total = volume(3, r, h1, h2);

//   and output volumes
 
cout<<" \n\n volume of cylindrical part = " << v_cyl <<" cubic meters"<< endl;
cout<<" \n\n volume of conical part = " << v_con <<" cubic meters"<< endl;
cout<<" \n\n         total volume = " << v_total <<" cubic meters"<< endl;
 
 
// hold the screen
 
cout<<" \n\n enter e (exit) to terminate the program....";
char hold;
cin>>hold;
}

//  definition of function volume
 
float volume( int choice, float radius, float hcyl, 
              float hcon)
{
// declare the local variables
 
float v;
   // variable used to store locally the calculated volume
 
if ( choice == 1)
       v = PI * radius * radius * hcyl;
else if(choice == 2)
   v = PI * radius * radius * hcon / 3.;
else if(choice == 3)
   v = PI * radius * radius * ( hcyl + hcon / 3. );
else
   { v = 0;
     cout<<" You entered a non valid choice. The value
             zero will be returned";
    }
return ( v );
 
}

/*      HERE IS THE OUTPUT
 
 
 
 volume of cylindrical part = 19.2664 cubic meters
 
 
     volume of conical part = 17.8902 cubic meters
 
 
               total volume = 37.1565 cubic meters
 
 
 enter e (exit) to terminate the program....
 
 
 */