/*
  Example on functions
____________________________________
  Jacob Y. Kazakia  jyk0
  Ocober 18, 2000
  Programming assignment
  Recitation Instructor: J.Y.Kazakia
  Recitation Section 01
____________________________________

Purpose: This program illustrates the use of a function which returns
         two values to the calling function.
         The main function provides the type and the length of a steel
         beam ( in feet ) and receives from the function weight the weight of
         the beam ( in pounds ) and an estimate of the error in the calculation
         of the weight.

  Algoritm: The algorithm of the calculation is described in the function
            weight below.

*/
#include <iostream.h>
#include <iomanip.h>


void weight ( int k, double length, double lerror, double& w, double& werror);

main()
{
  int    k = 2;        // The beam is of type 2
  double L = 12.4;     // the length of the beam in feet
  double E = 0.001;    // the(+ or - )error in the length specification  in feet
  double wbeam = 0.0 ; // the weight of the beam
  double werror=0.0 ;  //  the error (+ or -) in the calculation of the weight

  cout << setiosflags(ios::fixed) << setprecision (2);

  weight ( k, L, E, wbeam, werror);    // USING THE FUNCTION weight

  cout << "\n\n  The weight of the beam is : " << wbeam ;
  cout << " lb  with a possible  error of " << werror << " lb";

cout << "\n\n enter a character and hit enter to exit  ";
char hold;
cin >> hold;

 }

//   DEFINITION OF THE FUNCTION WEIGHT


void weight ( int      k,       //the type of the beam (input)
              double   length,  //the length of the beam ( input)
              double   lerror,  //the error in the length of the beam(input)
              double&  w,       //the calculated weight (output)
              double&  werror)  //the estimate of the error in the weight(output)

/*
Purpose: This function calculates the weight of a beam, from its length
         and its type.  It also provides an estimate of the error in the weight
         calculation.

Algorithm: In this function we consider only three different types of beams:
           Type 1:
                 s24x100     cross sectional area: 29.4 sq in.
                             with an error of (+ or -) 0.02 sq in.
           Type 2:
                 s10x35      cross sectional area: 10.3 sq in.
                             with an error of (+ or -) 0.01 sq in.

           Type 1:
                 c12x30      cross sectional area: 8.82 sq in.
                             with an error of (+ or -) 0.002 sq in.

           The specific weight of steel is  0.284 lb / cubic in.


           The weight of the beam w is calculated as:

           w = (length * 12 )* cross sec. area * specific weight

           The error in the weigth calculation is obtained by the difference of
           the weight so obtained and the weight obtained using increased length
           and inreased cross sectional area ( increased by the amount of error
           indicated).
  */
{
  double area;    // cross sectional area in  square inches  ( local variable)
  double aerror;  // error in crosectional area              ( local variable)
  double sw = 0.284;// specific weight in lb per cubic in.   ( local variable)
  double wplus ;    // the weight of increased dimensions    ( local variable)



  if ( k == 1)
              { area = 29.4;
                aerror = 0.02; }
  else if ( k == 2 )
              { area = 10.3;
                aerror = 0.01; }
  else if ( k == 3)
              { area = 8.82;
                aerror = 0.002; }
  else
              { cout << "\n\n  invalid  type  "  ;
                area = 0.0 ;
                aerror = 0.0;  }

  w = area * length * 12.0 * sw;

  wplus = ( area + aerror) * (length + lerror)* 12 * sw ;

  werror = wplus - w;



}
/*
         THE OUTPUT :


  The weight of the beam is : 435.27 lb  with a possible  error of 0.46 lb

 enter a character and hit enter to exit


*/