/* 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 symmetrically 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....


 */