roots_body

program lab1
use roots
implicit none
real(8)::x1,x2,xk,eps
real(8),parameter::mm1=1.4455,m2=0.5368,m1=1.0194,mm2=0.8813
integer::i=0,method
interface !If a procedure has another procedure as dummy argument then one has to specify its type, just as the type of other parameters.
          !An interface block is used for this case. It consists of the procedure statement with the definitions of its arguments.

    real(8) function f(x)
    real(8) :: x
    end function f

    real(8) function df(x)
    real(8) :: x
    end function df

    real(8) function d2f(x)
    real(8) :: x
    end function d2f

end interface
print*, 'Input x1,x2,and eps'
read(*,*) x1,x2,eps
if (f(x1)*f(x2).GT.0) then
    print*,'Error, f(x1)*f(x2)>0'
    stop
else
    continue
end if
print*,'Choose method (1-Newtons,2-Chord,3-Secant,4-Fixed-point iteration)'
read(*,*) method
select case (method) !Выбор метода
    case (1)
        print*,'Newtons'
        call kas(f,df,d2f,x1,x2,xk,eps,i,mm2,m1)
    case (2)
        print*, 'Chord'
        call hord(f,x1,x2,xk,eps,i,mm1,m1)
    case (3)
        print*,'Secant'
        call sec(f,x1,x2,xk,eps,i,m1)
    case (4)
        print*, 'Fixed-point iteration'
        call iter(f,df,x1,x2,xk,eps,i)
    case default
        print*, 'Error'
end select
print*, 'Results::'
print*, 'xk=',xk
print*, 'f(xk)=',f(xk)
print*, 'iterations-',i
end program lab1

    function f(x)
    implicit none
    real(8)::f,x
    f=exp(-x)-cos(x+4)
    end function f

    function df(x)
    implicit none
    real(8)::df,x
    df=sin(x+4)-exp(-x)
    end function df

    function d2f(x)
    implicit none
    real(8)::d2f,x
    d2f=exp(-x)+cos(x+4)
    end function d2f