How do I call my function in this program?

[mzdiva041986]

This is the program and I have 5 errors that I can't seem to get rid of, it was a Fortran 95 program that I had to translate into C++. could somone please help me.

#include <iostream>
using namespace std;

int main()
{
	//Declaration and Intialization
	float XL = 0.0;
	float XR = 0.0;
	float XS = 0.0;
	float X  = 0.0;
	float Y  = 0.0;
	float YL = 0.0;
	float YR = 0.0;
	float XB = 0.0;
	float XND = 0.0;
	float STEPSIZE = 0.0;
	float F;


	cout<<"What is the left-most interval endpoint?";
	cin>>XB;

	cout<<"What is the right-most interval endpoint?";
	cin>>XND;

	cout<<"What is the desired step-size for function evaluation?";
	cin>>STEPSIZE;

	XL = XB;

 do
 
	YL = F(XL);

	XR = XL + STEPSIZE;

	YR = F(XR);

	      if(YL*YR > 0)
		 {
			if(XR >= XND) break;
			{
		 
			XL = XR;

			YL = YR;}
		 }

			if (YL*YR == 0) 
		{
			if (YL == 0.0) 
		{
				cout<<"This is a root.";
				cout<<XL;
		}
				if (XR >= XND) break;

				XL = XR;
		}
			else
		{
			cout<<"This is a root.";
		                cout<<XR;

			if (XR >=XND) break;

			XL = XR + STEPSIZE;
		}


	                            if (YL*YR < 0) 
		{
		            XS =XR;
do
{			
	X=(XL + XR)/2;
	Y = F(X);
		if (YL*Y > 0) 
{
	XL=X;
	YL=Y;
}
				

	if (YL*Y == 0) 
{
	cout<<"This is a root.";
	cout<<X;

	XR = X;

	YR=Y;

}

	if (YL*Y < 0) 
{
	XR = X;

	YR = Y;

} 

	if (XR - XL < 0.00005) 
{
	cout<<"This interval contains a root.";
	cout<< XL,XR;

	XL = XS;
}
                if (XL >= XND) break;

}

			 
	while (XL<XND);

                float F;

	F = (X*X*X*X - 9*X*X*X - 2*X*X + 120*X - 130);



	return F;

}

The errors are:
F:\C ++ Numerical Methods\RF_BETTER.CPP(33) : error C2064: term does not evaluate to a function
F:\C ++ Numerical Methods\RF_BETTER.CPP(35) : error C2061: syntax error : identifier 'XR'
F:\C ++ Numerical Methods\RF_BETTER.CPP(37) : error C2064: term does not evaluate to a function
F:\C ++ Numerical Methods\RF_BETTER.CPP(77) : error C2064: term does not evaluate to a function
F:\C ++ Numerical Methods\RF_BETTER.CPP(127) : fatal error C1004: unexpected end of file found
Error executing cl.exe.

RF_BETTER.OBJ - 5 error(s), 0 warning(s)

[Narue]

Yea...post the Fortran code so that I have a point of reference for what you were trying to do.

[mzdiva041986]

This is the Fortran program:

program rf_better
implicit none

real::X,XL,XR,XS,Y,YL,YR
real::XB,XND,STEPSIZE

XL = 0.0
XR = 0.0
XS = 0.0

X = 0.0
Y = 0.0
YL = 0.0
YR = 0.0

XB = 0.0
XND = 0.0
STEPSIZE = 0.0

write(*,*)"What is the left-most interval endpoint?"
read(*,*)XB

write(*,*)"What is the right-most interval endpoint?"
read(*,*)XND

write(*,*)"What is the desired step-size for function evaluation?"
read(*,*)STEPSIZE

XL = XB

outer:do

YL = F(XL)

XR = XL + STEPSIZE

YR = F(XR)

if(YL*YR > 0)then

if(XR >= XND) exit outer

XL = XR

YL = YR
end if

if (YL*YR == 0) then

if (YL == 0.0)then

write(*,*)"This is a root."

write(*,*) XL

if (XR >= XND) exit outer

XL = XR

else

write(*,*)"This is a root."
write(*,*) XR

if (XR >=XND) exit outer

XL = XR + STEPSIZE
end if
end if

if (YL*YR < 0)then

XS =XR
inner:do

X=(XL + XR)/2
Y = F(X)
if (YL*Y > 0)then

XL=X
YL=Y
end if

if (YL*Y == 0)then

write(*,*)"This is a root."
write(*,*)X

XR = X

YR=Y

end if

if (YL*Y < 0) then

XR = X

YR = Y

end if

if (XR - XL < 0.00005) then

write(*,*)"This interval contains a root."
write(*,*) XL,XR

XL = XS

if (XL >= XND) exit outer

exit inner
end if
end do inner
end if
end do outer

contains

function F(X)

real::F
real,intent(in)::X

F=X**4-9*X**3 - 2*X**2 + 120*X -130

end function F
end program rf_better

[mzdiva041986]

I posted the Fortran code

[Narue]

>I posted the Fortran code
Really, I hadn't noticed. :icon_rolleyes: It's lunchtime where I am, so I was finishing my sandwich before I replied. Please don't bump your threads if you don't think your question is answered fast enough.

This compiles, but I didn't run it.

#include <cmath>
#include <iostream>

double F ( double X )
{
  // X**4-9*X**3 - 2*X**2 + 120*X -130
  return std::pow ( X, 4.0 ) - 9
    * std::pow ( X, 3.0 ) - 2
    * std::pow ( X, 2.0 ) + 120 * X - 130;
}

int main()
{
  double X, XL, XR, XS, Y, YL, YR;
  double XB, XND, STEPSIZE;

  XL = 0.0;
  XR = 0.0;
  XS = 0.0;

  X = 0.0;
  Y = 0.0;
  YL = 0.0;
  YR = 0.0;

  XB = 0.0;
  XND = 0.0;
  STEPSIZE = 0.0;

  std::cout<<"What is the left-most interval endpoint? ";
  std::cin>> XB;

  std::cout<<"What is the right-most interval endpoint? ";
  std::cin>> XND;

  std::cout<<"What is the desired step-size for function evaluation? ";
  std::cin>> STEPSIZE;

  XL = XB;

  while ( true ) {
    YL = F ( XL );
    XR = XL + STEPSIZE;
    YR = F ( XR );

    if ( YL * YR > 0 ) {
      if ( XR >= XND ) goto end;

      XL = XR;
      YL = YR;
    }

    if ( YL * YR == 0 ) {
      if ( YL == 0.0 ) {
        std::cout<<"This is a root."<< XL;

        if ( XR >= XND ) goto end;

        XL = XR;
      }
      else {
        std::cout<<"This is a root."<< XR;

        if ( XR >= XND ) goto end;

        XL = XR + STEPSIZE;
      }
    }

    if ( YL * YR < 0 ) {
      XS = XR;

      while ( true ) {
        X = ( XL + XR ) / 2;
        Y = F ( X );

        if ( YL * Y > 0 ) {
          XL = X;
          YL = Y;
        }

        if ( YL * Y == 0 ) {
          std::cout<<"This is a root."<< X;

          XR = X;
          YR = Y;
        }

        if ( YL * Y < 0 ) {
          XR = X;
          YR = Y;
        }

        if ( XR - XL < 0.00005 ) {
          std::cout<<"This interval contains a root."<< XL <<','<< XR;

          XL = XS;

          if ( XL >= XND ) goto end;

          break;
        }
      }
    }
  }

end:
  return 0;
}

[mzdiva041986]

thanks so much im not very good in C++ but i do try. Thanks again