! 4.2.f90
! 2024-10-08
! $Id: 4.2.f90 1.1 2024/10/26 14:02:16 s Exp $
! s , current spot rate curve
! s2, next year's spot rate curve

program a
implicit none
integer :: j, n
real(8) :: s(6), s2(6)
real(8) :: s_percent(6), s2_percent(6)

! input
data s_percent/5.0, 5.3, 5.6, 5.8, 6.0, 6.1/
n = 6

! calculating
s(1:n)  = s_percent(1:n) / 100.0
do j = 2, n
    s2(j - 1) = f_1(j)
end do
s2_percent(1:n-1) = s2(1:n-1) * 100.0

! output
print *, "4.2.f90"
print *, "current spot rate curve"
print '(6f5.1)', s_percent(1:n)
print *, "next year's spot rate curve"
print '(6f5.1)', s2_percent(1:n-1)
stop

contains
! function
real(8) function f_1(j) ! forward rate, i = 1.
    implicit none
    integer :: j
    f_1 = ((1.0 + s(j)) ** j / (1.0 + s(1))) ** (1.0 / (j - 1)) - 1.0
    return
end function
end program a
! end